mtyson

Having sunk many hours, parts and money into my '97 4.0 6 cyl 4x4 Cherokee...

It started having a hard-start problem that grew worse until it was quite scary to start the car, sometimes it would not start. Once it was running, it would run smooth and strong.

After research, replaced the IAC, no improvement.
Brought it to firestone to diagnose. They had it for several hours, said they could not reproduce.

I said, please try, it is stranding my family at times.

They called a bit later and said, OK, we kept "doing things to it", and now we believe you have crankshaft sensor that is bad.

I go to pick up the jeep, and (having paid them almost $100 to diagnose), the jeep now has a CEL and is running very poorly.

The manager shrugged his shoulders and waved me off... email already sent to area manager...

I brought it home (limped it home) and replaced the CPS...

Hard-start issue DOES appear to be resolved, however, rough running issue remains:

After startup, in park, you can feel the jeep sort of shuddering back-and-forth, and smell bad exhaust with a strong unburnt gas smell in it. Putting it into gear, you can really feel the jeep rocking, maybe around 5 cycles per-second, whole jeep rocking, feel it in steering wheel, everywhere...

Can also smell gas smell in engine compartment...

That's what I get for bringing it to the "pros" and paying a premium...

Good people of cherokeeforum... any thoughts or advice?

mtyson

BTW, when I disconnected the battery to do the CPS, the CEL went off, and has never come back... I did the three-turns-of-the-key trick, and no codes showed...

If I pull the oil dipstick, I can smell some gas in there.

BlueRidgeMark

First of all, Firestone is NOT "the pros". They employ bottom feeders. They are NOT skilled mechanics. Same for Pep Boys or any of the other national chains.


To find a good mechanic requires some research. Word of mouth is your friend. Consult review sites like Yelp. Ask local 4WD clubs.

If you can find someone in the business, like a tool salesman (Mac, Snap-On, etc.), ask him. They often know who is who and what they do.

Your car is running stupidly rich. That can be because of a bad O2 sensor, a vacuum leak, or several other issues.


Firs thing to do is to go to Autozone and ask them to read the codes, then report back here.

Also, do a search on this site for "TPS test". I found this on doing the same on the Grand Cherokee, and it's the same test, so this should do it for you. One thing, though. This test is better done with an analog voltmeter (has a dial and needle) rather than the DMM (Digital Multi-Meter) as show. It's easier to see if you have a smooth sweep of the voltage on the analog dial. You can use large safety pins to back-probe the connector.

OldTires

X 3 on what Mark says.

rzldzl

several hours of diagnosing for $100 is paying a premium?

wheres your gofundme?

investinwaffles

Ok, I'm not going to jump on the hater bandwagon but when you pay for crap service at a "parts changer" (Firestone, Brakes Plus and similar), your gonna get crap service.

The true value in a qualified and pedigree'd mechanic is their troubleshooting. Most of the time it will save you time and money over the budget solution.

That being said, it sounds like MAP or TPS sensor related. I have several spares of all sensors which makes troubleshooting easy

But unfortunately not a whole lot of info to go off of. If you are truly only $100 in the hole, find a GOOD mechanic to diagnose. Preferably one that lives and breathes Jeep 4.0's - they are always around.
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Willys55

Not for nothing, but Firestone did not break your jeep, you took it there broken. Also why blame the whole place for the actions of one tech?

I grow tired of people throwing stones at others because they had a "bad experience"
You either need to ask around and find a shop that is willing and able to help you, or learn to repair it yourself by asking the questions here and following the sound advice given to you.

mtyson

Heading to autozone now. I put in a new TPS a few months ago, but I'll check it out too.

Thanks for the help, this is the second vehicle that has come back from Firestone in worse shape (should have learned the first time, I know).

BRB with some codes.

mtyson

AZ says, no codes. CEL is off.

I am checking TPS now.

mtyson

OK, not the TPS.

We are thinking O2 sensors. Researching that now....

Martlor13

What brand tps did you use and how are you checking it?

mtyson

After replacing TPS (duralast) and upstream O2 sensor (bosch), there is no change...

Any ideas?

mtyson

After a day and a half of troubleshooting, I decided to check the sparkplugs, even though they are new.

The first wire I pulled off the cap came completely out in my hand.

Firestone had failed to connect it to the engine. It was ON it, so it APPEARED connected, but it wasn't pressed in.

Tell me... intentional?

I think the biggest problem with most shops, and the biggest advantage of us do-it-ourselfers is:

GIVING A CRAP

Thanks everyone for your support... I am super relieved.

fb97xj1

Mopar TPS and NTK o2 sensors are all my 97 will ever use. Havent messed with the MAP yet, but its still Mopar.

I doubt the loose plug wire you found was intentional. Ive overlooked that at least once on my own vehicle. Sometimes its the little things that get you.

mo8414

Just an fyi I replaced my 02 sensor in a cavalier with bosch and all 4 that we tried were no good right from the store. Put a different brand in from a different store and it was good to go. Used a machanics computer reader to determine the bosch ones were junk. Never again well I use bosch.