Why is my GTI doing this to me?

This problem with my GTI is driving me CRAZY!!! I'll be driving along on the highway, and the engine will suddenly and completely lose power. There is absolutely no response from the accelerator. When I coast to a stop at the side of the highway, the car returns to idle as if nothing happened. This may happen again in a few minutes, hours, or days. It's completely intermittent and can't be duplicated in my garage. I also note that the car feels a bit sluggish, and tends to stall now and then when the clutch is released at stop signs, etc.

I've also noticed that it seems to take longer than it used to for the car to start, as if fuel pressure is taking more time to build up or system pressure is not being maintained after stop. I just recently replaced the fuel line to cylinder #1, and I was surprised that there was pretty much no fuel pressure at the fuel distributor when I loosened the banjo bolt. The car had been off overnight, but I still expected a little pressure.

This is what I've done so far so far:

- Checked for vacuum leaks, rips, tears in the intake; none found.

- Checked for fuel leaks; none found.

- New sparkplugs, wires, cap, rotor.

- New ignition switch.

- New fuel injectors/o-rings.

- New fuel pump relay.

- New fuel filter.

- Checked timing; okay.

- Almost new in-tank (transfer) fuel pump; no loud buzzing at main pump.

I really don't have the gauge and fittings required to check fuel pressure, but since the problem is intermittent I'm not sure it would tell me anything. The main pump is about 10 years old, so I'm going to go ahead and replace it too. If that doesn't do the trick, I'm not sure what else to do! What about the coil? HELP!

Reply to
Kent
Loading thread data ...

Since GTIs have been in production off and on for 22 years, with 4 generations, it would be useful to share the basics: Year model to start with.

Reply to
Rex B

Sorry, this information is usually included in my autosignature. Car is 1987 VW GTI 8V, Engine Code RD (CIS-E/KE-Jetronic).

Reply to
Kent

that sounds like the engine's "security mode" kicking in.... is the engine stock?

Reply to
ruimigueldias

Security mode? Please elaborate. If you're referring to the malfunction of an anti-theft device for engine cut-off, it doesn't have one. It's a stock

87 GTI 8V.
Reply to
Kent

Jim B.

Reply to
jimbehning

You need a new coil pack. These almost never fail all at once so I would replace just the one that failed and you will be fine. TL

Reply to
Tom Levigne

These symptoms do not sound like coil pack to me.

If I follow the description correctly, it is as if he had removed his foot from the accelerator, tho he had not.

Reply to
Tom's VR6

I agree. Besides, the '87 didn't have coil packs, it had a single, conventional coil.

Reply to
Randolph

If you have a o2 sensor in there try running without it ( disconnect ).

SFC

"Kent" schreef in bericht news: snipped-for-privacy@corp.supernews.com...

Reply to
SFC

It sounds like the fuel pump.

Andy

Reply to
Nik&Andy

Methinks thou mayest be in need of a new distributor or a new Hall Effect Sensor (pickup) on the distributor assembly. Also, take it to a mechanic and have a fuel pressure test since you seem concerned about this, but I doubt its your problem.

Oh yeah, on a car that's this old (pushing 20 years no?), I would have the exhaust system checked out, specifically the catalytic converter which may be broken or plugged. What can happen is the little screens inside break off due to the accumulated effects of temperature and vibration, they can wedge together creating a plug. Of course, this may not be your problem at all, but I did have that problem on my car ('95 Jetta GLS) and it would totally kill power since the engine could not exhaust. The car would idle okay since the engine could squeeze a small amount of exhaust through the remaining portal, but giving it some gas would cause it to bog down in a most distressing fashion.

Yes it was intermittent for a fashion, but then one day it became permanent, on a Friday afternoon, at 5:10PM, in the middle of a 4-way intersection. It was great fun pushing the car through the intersection, fortunately another driver did get out and help me. I could start the car, it would idle, but putting it in gear and giving it some gas cause it to lurch forward a few inches then die.

Reply to
Pierre_St_Germain

You think that the fuel pump suddenly pumps only enough fuel to idle, and then suddenly returns to full capacity?

Reply to
Tom's VR6

I'm not sure about a CIS car but would think it's not that different than Digifant as far as fuel pumps are concerned. The fuel pump gives more than enough fuel for any running condition. On a Digifant car the fuel pressure regulator is vacuum-activated according to the engine's need for fuel and it routes any unnecessary fuel back to the tank. On a CIS car I'll bet the fuel distributor probably does a similar thing...the pump provides constant pressure and probably the fuel distributor determines how much fuel to send to each injector and then the excess is sent back to the tank.

However if the pressure from the pump is too low, it's possible that the engine is getting enough fuel for idling but at higher loads/speeds the car might not be getting enough fuel anyway.

Reply to
Matt B.

And if that were the case, I suspect flooring the throttle with a limited fuel availability would probably stall the engine rather than having it idle. That would be a form of "response".

Reply to
Tom's VR6

Yes but it does depend on how he's "coasting" to the side of the highway as he said. If it's shifting to neutral before the engine totally stalls it might have time to recover to idle speed w/o stalling. Or if he's leaving it in gear and takes his foot off the gas the car could also be restarting itself. It'd stall probably only if he continued to leave it in gear and mash the throttle to the floor but if he's taking his foot off the gas

*very* soon after noticing the power loss or shifting to neutral very soon, that might prevent an actual stall.
Reply to
Matt B.

I have once been able to drive ~50 miles home with a failed transfer fuel pump ('87 Gti 8V) The car would idle just fine, cruising at 50 mph on flat road was no problem, but going up hill or going faster, the car would sputter and loose power.

Reply to
Randolph

Interesting development in my troubleshooting of this problem over the last few days. Many of you may know that the KE-Jetronic CIS-E system on my car includes two throttle switches, one for full throttle enrichment/RPM limitation, and the other an idle switch for deceleration fuel shutoff. The idle switch also provides input to the idle stabilizer valve. Whenever the throttle valve is closed such as when decelerating or coasting, the idle switch is closed (continuity), sending a signal to the computer. If the computer receives this signal AND engine speed is above 1600 RPM, the computer cuts off fuel to the injectors by reversing current to the differential pressure regulator. Fuel flow is then restored by the computer once the engine speed drops below 1300 RPM. This function is intended to improve fuel economy.

Well, it seemed to me that a malfunction of the idle switch might be sending erroneous signals to the control unit, resulting in fuel cut-off at inappropriate times. So I thought I would check out the idle switch (which is buried out-of-sight under the throttle body) to see if anything was amiss. First off, I noticed that the full throttle switch made a very definite clicking sound when engaged. I expected the idle switch to do the same, but it didn't. I then removed the throttle body to get a better look at the idle switch. It was almost completely covered with grease and grime. (Long story, I recently repaired a leak in the intake system at the bypass hose for the air-shrouded injectors. It exits from the bottom of the rubber bellows that connects to the throttle body. Not only was this leak allowing unmetered air to enter the system, but small amounts of oil from crankcase ventilation was exiting in the vicinity of the idle switch. I didn't notice this when I repaired the hose as I removed the bellows and repaired the connection off the car).

I cleaned the idle switch as well I could, and after poking it a bit, the plunger started to make the clicking sound I expected. I checked for continuity when the plunger was in, and it checked out. When I reassembled everything, I left the throttle switches disconnected just to see if the power loss problem recurred. I've driven the car over 250 miles since then, in all kinds of traffic, and the problem has not recurred. This is by far the longest I have gone without the power loss problem since it began many months ago. Not only that, but the car no longer stalls at stop signs. Sure, the idle bounces around a bit since the ISV isn't receiving the proper signal from the idle switch, but the car never comes close to stalling.

I definitely think I'm on to something here. My theory is that the idle switch was malfunctioning by intermittently sending a closed signal to the control unit even when the throttle was open. This behavior was probably caused by a combination of wear (it's the original switch), oil/dirt contamination, and engine vibration. Since the RPMs would be well above 1600 (especially while cruising down the highway, where the problem tended to occur) the erroneous signal would cause the control unit to cut off fuel to the injectors until engine speed dropped below 1300 RPM. This is why the car always returned to a proper idle after I coasted to a stop by the side of the road, or pushed in the clutch to disengage the engine from the drivetrain. If I just let the engine turn with the wheels while frantically pressing the accelerator, power would not return.

I'm going to drive around for a week or two with the throttle switches disengaged just to make sure I've isolated the problem. Once I'm satisfied that the problem is gone, I'll install a new idle switch. I'll provide an update indicating success or failure at a later date. Right now I'm optimistically assuming success.

THANKS TO EVERYONE FOR THEIR THOUGHTFUL CONTRIBUTIONS TO MY TROUBLESHOOTING, ESPECIALLY THOSE THAT SENT DETAILED RESPONSES TO MY EMAIL. YOU DEFINITELY GOT THE WHEELS IN MY HEAD TURNING. I COULDN'T HAVE DONE IT WITHOUT YOU.

Reply to
Kent

Good thinking! And thanks for posting back, reading (pending) solutions is always interesting, not to mention educational.

I had the opposite problem about a year ago, my idle switch was broken and would never close. This caused idle to be way out of spec, particularly with the A/C on. From the dealer you can get the switch only with the full throttle switch and the wiring harness, priced the wrong side of $100.

At the junk yard I found a number of CIS-e engines, but they all had broken idle switches. If you are handy with a soldering iron, you can use the switch from a Digifant engine. (The California variety of Digifant (I?) uses switches, I believe the 49 state variety (II?) uses a potentiometer). The switches are the same as CIS-e, but they are wired differently. For Digifant the two switches are wired in parallel and the connector is 2-pin. CIS-e uses a 3-pin connector. I cut the idle switch out from my harness and soldered in a "new" one from a Digifant engine.

Reply to
Randolph

Other way around (sort of).

You are correct that California is Digifant I and 49 state is Digifant II. But it's Digifant I that uses the potentiometer and II that uses the switches.

And this distinction only applies to 1991-1992 vehicles. 1990 and older Digifant cars were Digifant II nationwide.

Reply to
Matt B.

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.