Loss of power 91 jetta 8valve

and how is your cat. conv.? Maybe it is partially clogged?

How did you check the ECM? Ohm meter at it's plug to check the sensors out?

good luck, dave (One out of many daves)

I am not sure how the ECM was checked, my father did that after I left for school (break ended). As for the cad. converter, there is plenty of pressure coming out of the exhaust. Also wouldn?t a partial cloged converter show up on an emisions test? (which was run just after I bought the car)

Thanks for the input.

-Josh

Well if you just bought the car and it passed the emissions AND it was running this way...........How do you know you have a loss of power?

Well back to the basics.... Check compression.....maybe even a leak down test Examine spark plugs well and make sure that they are gapped properly. Check timing and advance since that will tell you the condition of the knock sensor. The knock sensor will give you a big loss of power if it is bad or not torqued down correctly. Check vacuum since a leak could cause your problems too. Oh and get a Bentley for your vehicle. I think someone has a website dedicated to the Digifant II system if that is what you have on your CA equipped Jetta.

Hope this gives you a few leads. ;-)

"One out of many daves" wrote: > Well if you just bought the car and it passed the emissions > AND it was > running this way...........How do you know you have a loss of > power? > > > Well back to the basics.... > Check compression.....maybe even a leak down test > Examine spark plugs well and make sure that they are gapped > properly. > Check timing and advance since that will tell you the > condition of the knock > sensor. The knock sensor will give you a big loss of power if > it is bad or > not torqued down correctly. > Check vacuum since a leak could cause your problems too. > Oh and get a Bentley for your vehicle. I think someone has a > website > dedicated to the Digifant II system if that is what you have > on your CA > equipped Jetta. > > Hope this gives you a few leads. ;-) > -- > later, > dave > One out of many daves. > > > >

Well I am no expert on jettas, or any car, however I had an 87 Cabriolet with a 1.8L 8valve that would tackle hills at 70mph+ This jetta barely makes 60 in thrid gear (5 spped manual) on the same hill. There is not much of a weight difference between the two cars ( I checked), so I know it?s not because the Jetta is significantly heavier. The other thing is that there is a slight hesitation when you put your foot down.. there is a very noticible response time. The reason I believe there is a loss of power is beacuse if an engine with the same displacement yet older style fuel injection (as in no computer) can perform one way, it stands to reason that this engine should be at least as good. Checking stock specs the 1.8 in my 87 had was rated at 90 hp (i forget the rpm) and the 1.8 in the Jetta is rated at 100hp.

Again thanks for the input.

-Josh

So if it is generally slow make sure that the timing belt is correctly installed. I have seen quite a few off by one notch. The engines still run but are sluggish like what you describe. Usually the 91 1.8 engines are quite peppy when it is working correctly. Also make sure that the timing belt tensioner is turned clockwise to tighten belt.

let us know what you find, but check that T-Belt first. Really easy to check too! ;-) later, dave (One out of many daves)

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I think you may be on to something with this. When I purchased the car I found a service manual (cover looks similar to that of a Bently) in the trunk. In the manual were print outs of another manual concerning the installation of a timing belt. These prints were in the same section in the maunal. I have a feeling that the timing belt was replaced. I didn?t even think to check to see if it was installed correctly, I figured if I hadn?t been the car wouldn?t have run at all.

Thank you!

-Josh

"dave AKA vwdoc1" wrote:

correctly

WELL go out and check right now!!! lol Just kidding. ;-)

let us know what you find and take your time checking the timing belt. later, dave (One out of many daves)

"dave AKA vwdoc11" wrote: > WELL go out and check right now!!! lol > Just kidding. ;-) > > let us know what you find and take your time checking the > timing belt. > later, > dave > (One out of many daves) > > "dubljay" wrote in message > news:1_588056 snipped-for-privacy@autoforumz.com... > >I think you may be on to something with this. When I > purchased the > > car I found a service manual (cover looks similar to that of > a Bently) > > in the trunk. In the manual were print outs of another > manual > > concerning the installation of a timing belt. These prints > were in > > the same section in the maunal. I have a feeling that the > timing belt > > was replaced. I didn't even think to check to see if it was > installed > > correctly, I figured if I hadn't been the car wouldn't have > run at > > all.

OK, I really don?t know what to think now. I checked the timing belt.. and it couldn?t be more perfectly alligned. So now that is ruled out. I double checked the fault codes for the Digifant I computer, (bridged the two connectors under the shift cover and check engine light blinked for the codes). got 4 4 4 4, no fualts. When poking around the distributor I broke the Hall sending unit... I replaced the whole distributor with a used one, Hall sending unit and all. Set the timing as per Bently. End result even less power. Now the damn thing drives like the hand break is on. With the accelerator to the floor in first gear I hit about 5500 rpm and about 25 mph. When I let off the accelerator or down shift it sounds like it is backfiring in the intake. There is no problem with starting, there is an intermitent surging at idle, of about +/-300 RPM (which was also a problem before replacing the distributor and hall sending unit). What in the hell do I do now? The plugs, wires, rotor, cap all seem to be fine... should I replace them anyway? Could the computer itself be toast and still give no fault readings? Could there be bad wiring between sensors and the computer allowing for a no fault reading? I checked the torque on the knock sensor mounting bolt, and reset it to

13 ft-lbs. I have the sinking suspission that this is not the original engine for the vehicle, I double checked to make sure that it was indeed an RV engine, which it is. If it is not the original engine would that cause a problem for the Digifant I computer? Is there anyway to tell if the engine is indeed the original one or if it is a replacement?

Thanks for the help

-Josh

Visit Topic URL to contact author (reg. req'd). Report abuse: Could it be a blocked catalytic converter? ... and wouldn't a 91 have Digifant II or is it a California car or something?

how did you set the ignition timing? did you check the ign advance which should check the knock sensor operation too? did you check the fuel pressure regulator since it may be allowing fuel into the intake manifold? Did you check the air flow box? Are you sure you have the firing order correct on the distributor? You also need to check the TDC mark on the flywheel with the position of the #1 piston!

Time to check the wiring and sensors going to the ECM at the ECM's plug!

good luck, dave (One out of many daves)

Maybe the previous owner also had some work done on the camshaft or head.

Make sure that the cam sprocket is the right way around. If timing appears to correctly set up according to Bentley, yet has poor power until you get to almost 5000 rpm, then the sprocket is probably reversed so the wrong marks line up resulting in cam timing being retarded by some 30 degrees.

Check the sprocket orientation to make sure it's not on back to front -- or inside-out -- whichever way you think of it.

Another "quick" check is to check the cam lobe positions. At TDC on cylinder 1, a straight-edge placed diagonally across the lobes should be parallel to the top of the head.

Digifant has a habit of doing that!

You will need to make sure the ECM/ECU numbers are exactly alike. Just post the numbers you find on yours here too.

I doubt if it is the ECM but it might be. I think I have replaced one Digifant II ECM where the vehicle did not start at all. I am not sure why this one went bad, but all has been well for years. Did you test all sensors/switches at the ECM harness plug? Very important to check those grounding wires!!!!

Are you sure you have an exhaust that is not clogged? Check the vacuum with a gauge during different engine loads (idling, part throttle, full throttle and deceleration). Post results!

Are you sure you checked the ignition very carefully while checking the spark advance? That will tell you if the knock sensor is working correctly. If it is not working correctly then you will have a loss of power while accelerating.

Not sure if your CA equipped Jetta has an EGR valve. Maybe that is a test pipe you are looking at. If it has a rubber cover over it's tip you can remove it to see if the exhaust comes out of it slowly or almost like a tailpipe. (Another test for restrictive exhaust)

Time to think about taking this Jetta over to a good VW shop so you don't spend unnecessary $$$. ;-)

JMHO dave (One out of many daves)

Acutally I have given up. I was right they have replaced the engine, and in doing so they have cliped wires and connectors off leaving me no way to tell what is what. Anyone want a 91 jetta parts car? I would take it to a shop however there isn?t a mechanic within 100 miles that i would trust to work on a VW.

Get a Bentley, a Multimeter and some time. Do it yourself....................You can!! ;-) You will gain a lot of knowledge about your Jetta and a lot of satisfaction when you find and repair the problem(s).

I?ve got a bently, and a multimeter... however a good portion of the wires are not even the correct color so I really dont know how i can trace or test them.

Yeah I am not sure about those California cars. :-(

I usually have to test the resistance of wiring from the ECM to where ever it goes to. I don't always trust those wiring diagrams too. I sometimes make mine own just in case the books are wrong. I had to do this for my 91 Passat auto transmission's valve body.

Oh and I have seen a bad AirFlow box causing a lack of power with one Digifant II vehicle. Or a dirty filter (fuel or air).

good luck, dave (One out of many daves)

"dave AKA vwdoc11" wrote: > "dubljay" wrote in message > news:1_601583 snipped-for-privacy@autoforumz.com... > > SNIP > > I've got a bently, and a multimeter... however a good > portion of the > > wires are not even the correct color so I really dont know > how i can > > trace or test them. > >

I have a 91 jetta, manual, same engine (RV), same problem. I also suspect my motor has been replaced, because the title says its a rebuild and that it?s exempt from odometer readings. (although I dont see any clipped wires around the engine)

I have tried the basics, just like Dubljay. when I got this car it ran fine. there were a few rare times where it would stall out and wouldnt start, but then this problem developed over last winter. now, it starts right up, and runs forever at idle (until i stall it), but there is significant loss of power, it acts like there is a clogged fuel filter on acceleration, (during which sometimes initially it floods and dies immediately at a slight touch of the gas),. it will accelerate fine for a few seconds,, but then power will fade almost completely, and then usually the car will start bucking, or power comes back in the higher RPM range, or the car stalls, and wont start. one characteristic of this problem is the surging of the throttle. I know the car is going to lose its power when when I take it out of gear to shift and the engine maintains a high RPM, or the throttle surges at idle sometimes maintaining an idle of 1800 rpm?s or so, or just surging from 900-1400 rpm?s up and down, then dipping down to

400-800 either stalling, or almost stalling.

The car has always seemed to run too rich. when I first got the car, I failed emissions tests so I replaced the Oxygen sensor about 2 years ago which helped thin the fuel mixture, and it passed ( I didnt drive it much even when it ran)

When this problem started: First I replaced the fuel filter (lifetime my ass) I have a fairly new air filter too I replaced a while back (K & N), and i replaced the checker auto spark plug wires with Bosch wires. that didnt help so I took this into VW mechanics shop where they tested the fuel pump, put on new spark plugs, checked a valve and some sensors, but they couldn?t figure out what was wrong, so after around $200 of labor, so I had them stop. at this point the car would only do a dead stall, it didnt do any bucking or jerking, it would just unpredictabley lose power slowly and stall, So I could still drive it around I would wait until it was cooled off then it would *usually* start again. then my radiator fan switch went out, and I thought it would be a good idea to change the cap and rotor when I changed out that heat sensing switch on the radiator. The old cap was not bosch, and and it was worn, so i put on a genuine bosch cap and rotor. If you can believe it, this is when the bucking and surging started ! I expected the new cap to help get back some power, and maybe help with the stalling, but instead it made things worse, now I had even more power loss, except when it hit the high rpm?s it would give me back the power I once had, (still not to the engine?s potential, I never had that), then I would need to shift, and it would repeat all over again. this effect of power kicking in at high rpm?s slowly wore off, and all the while the car would sometimes crap out and not start. So during that time I had a friend do a timing check at his acura shop, he said the timing was fine, and gave me two suggestions: Air flow sensor, or a clogged cat. so I went to the foreign wrecking yard and the owner helped me try several parts, my airflow sensor tested ok to me, but thats what we tried first ( got one off a 91 fox). same resistance readings, and no change in the condition. Next we tried the Ignition control module on top of the ECU housing, no change. then we tried the selenoid by the intake manifold, which i think is the EGR valve, because one hose went into the intake manifold, I cant remember where the other hose connected to (crankcase?), Still no change, so we put in a brand new in-tank fuel pump, I had a little better throttle response after, but the same sputtering occurred. then the junk yard owner suggested I try taking off the gas cap and running it, well I did have the wrong cap on, one that didnt allow air to get in, (my sister had driven the car, and she had changed the old cap for some reason) now with the gas cap off, the car didnt sputter or stall, (it sometimes has to run for a while before it begins sputtering, but I drove for a few miles, and everything was good) much to my disbelief, and I drove home from the junkyard thinking the guy was pure genius. I found my old gas cap, that seems to be a breather cap, and put it back on, (though not tightly). most days the car still didnt have the power it originally did, but somedays it would get back to its old peppy self. that great solution lasted for less than 2 weeks, and now it is as bad as ever :(

I am so grateful for your site where I found the same problem on the same engine. I do take off the gas cap when it starts sputtering but that doesnt help now. So after reading your suggestions yesterday, at a muffler shop I had my tailpipe cut off at the catalytic converter to test for clogs, they couldnt find anything wrong with air flow there, and they tried to diagnose the problem but couldnt find anything. I dont have a bentley manual, just a cheap one. I would appreciate any suggested solutions to this problem, I dont think it is timing or engine related, I was looking to replace the distributor next, until I read here that that hadn?t helped dubljay. I am guessing that it is some other electrical problem, or and issue with the fuel lines and/or the accumulator/regulator for those fuel lines. but right now I dont have the money to get a manual on top of the part(s) I need.

Thank you for your time and ideas,

Steve.

Ok its been a while. I got the power back... hehe I?m gonna have to be careful when driving it now, I don?t need speeding tickets.

My currnet problem now is that it surges badly, not just at idle either. I can feel the engine surge while under load, when i down shift, and when it idles. When idling it surges so bad that it causes the check engine light to flicker on and off. a few times the surging was bad enough while normal driving that the knock sensor kicked in and dropped the rpms and power way down.

On the throtle body there is that adjustment screw that is supposed to be pluged (the one you are not supposed to adjust) well the previous owners have the plug removed and i think that the screw has been adjusted. any thougts?

also its mid summer here, hot as hell out and the temp gague doesnt really get up to normal while driving, it hovers around the colder side, unless idling for long periods. is the gague screwed, the themostate, or the sensor bad? I was under the impression that VW?s generally run hot.