1998 Jeep Cherokee power loss, missing, no codes...TPS??

Hey y'all;

I've got one of those "mystery problems," could use some help. I drive

98 Cherokee Sport, 4.0L inline 6, with manual transmission, around 110K miles. The problem I have is this: at about 2000 RPM, the engine loses power and sometimes misses. During the latter incidents, it acts as though its not getting enough fuel, something like the beginnings of a fuel pump dying but not as severe. The problem is more pronounced if under load (AC on, carrying heavy stuff, going uphill..) or in higher gear ranges, and seems to be worse when the outside air temperature changes rapidly. Gas mileage has dropped by about 5-6 mpg since the problem started.

So far, several visits to the dealership have been fruitless. There are no codes being generated, so there's not much to go on. The oxygen sensor was replaced a few months before the current issue started due to a different problem, and the throttle body & connections thoroughly cleaned then, too. The dealership tried to tell me I had "weak valve springs" and needed a complete engine overhaul ($800+) to replace them, which did not sound right to me at all. I've had a lot of trouble finding a good garage nearby, so I'm ready to start tinkering myself in what little spare time I have. :-(

I've seen a lot of stuff on here about bad TPS sensors and/or bad connections, could this be the cause of my problem, too? I don't have a big toolkit nor am I terribly knowledgeable about fuel systems or testing voltages and such, so I'm not sure how best for me to start working with this. I bought a Haynes Manual a long time ago, but it doesn't have much info in it about sensors & such for the 1998 model (& newer).

Also, just recently, it has started with a new problem: when I turn on the left turn signal, both lights blink as though I'd turned on the hazards. Doesn't happen with the right blinker, doesn't happen if the ignition is off and the car parked, only when running & in motion. Almost simultaneously, the rear passenger electric door lock mechanism began malfunctioning, and refusing to lock or unlock while making a nasty grinding noise. I have no idea if these problems could be related in any way (grounds gone bad? shorts? lightning? ) but I just wanted to mention them in case they are clues.

Thanks for whatever help you can offer.

Reply to
katuah
Loading thread data ...

Reply to
L.W.(Bill) Hughes III

Someone else on this group had one of the engines with the bad valve springs. Jerry B I think....

There are some engines out there with the bad springs, that's for sure.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Reply to
L.W.(Bill) Hughes III

If all you need is new springs you can do that yourself.

They make adapters that thread into the spark plug holes that use air pressure to hold the valves closed and you can compress and remove the old ones with the head still on the engine.

If you think you may need or benefit from a valve job you can pull the head in your driveway and have your corner machine shop work on the head and you reinstall it.

The labor involved is pretty straightforward and you can save yourself a ton of labor charges.

Reply to
billy ray

My 97 i6 has acted similarly. I have had others describe my problem as weak springs also. I have also left mine with the dealership for days, only to get back the same jeep problem (but $150 poorer..). The last time I tried that was a couple years ago. They didn't believe in the weak spring thing, they thought it would act the same way all the time if that were the case, not just high rpm and under load. I don't believe them. Still seems like weak springs. I know the best way to get by this is to replace the spings. What I have done is to use Seafoam. I pour about half a can slowly in the throttle body at idle (or a little above idle), add the rest to the gas, and I am 'cured' for about a year. ( Follow instructions on the can.) I tried the new plugs and wires suggested by the dealership, and this is the only thing that has worked for me. Of course, if you have the cash or time, replace the springs. Especially since with this cheap fix , you're never really sure about that trip to the mountains......

cal

Reply to
Cal

Be aware you may have to clean or replace your spark plugs after the SeaFoam Treatment.

Reply to
billy ray

I had the same symptoms with my 90 XJ, it was the O2 sensor. I would double check the connection, all connections for that matter as they have always been a problem on XJ's.

Reply to
JRK58

The O2 sensor for the Renix system on the 88-91 XJ is under recall!

If you haven't had the recall done it is a freebie still.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Hey Bill;

I have to ask, what is the defining thing to make you believe it is the springs? I ask because I had thought that weak springs would cause "clacking" if they weren't doing their job, sort of like a redlined/overrotated engine, only starting at lower RPM's, but this problem appears primarily at only around 2000 RPM (which seems really low), and actually seems to lessen at higer RPM's (22-2500).

Is there a way to know besides the coded diagnostic, because the computer tester at the dealership showed nothing of the sort - actually, showed nothing at all, per the mechanics there.

Reply to
katuah

Mike - where did you see the recall? I definitely need to check on that. I know the O2 sensor was already replaced once, but if it is a problem part, maybe it got replaced with another problem part, since it was done at the dealer. (heck, wonder if could get a refund...)

I've really been wondering if it wasn't some sort of air temp sensor, isn't there one on the intake manifold? since it does seem to be a fuel mix problem AND changes severity with air temperature.

Mike Roma> The O2 sensor for the Renix system on the 88-91 XJ is under recall! >

Reply to
katuah

They found the recall after they failed me 3 times on emissions and I had paid the extortion fee to get a conditional pass. The computer refused the conditional because of the recall. LOL!

I gave them shit for not checking that 'before' fixing 'ghosts' so they gave me the 2 emissions retest costs back at least. With the new O2 sensor, it passed easily.

I have sense been told and it is posted somewhere about the recall. It's >

Reply to
Mike Romain

Reply to
philthy

How does seafoam in the FUEL SYSTEM cure weak valve springs for a year??? You've got worn valve guides that are cruding up your valves and restricting flow maybe... or perhaps you've got really really bad carbon buildup that's causing ping (which will definitely be folowed by some power loss), hell maybe you've got carbon so bad that it's shrouding your valves and reducing flow... In which case some hard wide open throttle runs every once in a blue moon should help. but nothing in your fuel, intake, or combustion chamber is ever EVER touching your springs or effecting them in any other way.

Reply to
Simon Juncal

You've got an odd electrical problem and your 02 sensor was recently replaced.... look at these two WAY before you take the valve cover off.

Reply to
Simon Juncal

Katua; Mike is talking about 91 and earlier he obviously didn't notice you wrote that you have a 98, they have completely different fuel injection systems.

Reply to
Simon Juncal

oh, really..... I never said anything about curing the springs. It 'cured' the misfire. you're reading between the lines. I can't believe you actually thought someone would think it 'cured' the springs. If I had anyone else even remotely thinking that I believed I had 'cured' the springs, then I apologize. And yes, carbon on the valves, and the cylinder head, is what it cleans. cal

"Sim>> I know the best way to get by this is to replace the spings. What I have

Reply to
Cal

What are you blathering on about? I most certainly did qualify my statement with "on the 88-91 XJ" in response to JRK58's comment about 'their' 90's O2 sensor.

Maybe katua didn't 'read' my statement, you sure as hell didn't!

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Read Katuah's reply to your advice to JRK, then read your immediate reply to Katuah later on the same day. BEFORE you get your panties all in a bunch.

Here let me piece it together for you:

1) you replied to JRK about the recall 2) Katuah replied to that post and said "where did you see the recall? I definitely need to check on that." 3) you replied to Katuah and did not correct them, you mentioned nothing at all about the fact that Katuah need not look into that recall... 4) So I did, hopefully saving Katuah some fruitless searching. because you were too busy sharing your fond memories of emissions tests past.

5) like we need one more "battle story" of your past "victorious" emissions tests.

Reply to
Simon Juncal

I don't know that the person doesn't own an 87 to 91 Cherokee 'also' like they were asking about on the recall so I replied like asked.

I was 'very' specific in my post, you implied otherwise.

Mike

Sim>

Reply to
Mike Romain

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.