Michael Luce

I have a 95 Grand Cherokee Limited with the 4.0L. When I first start it up its idles at around a 1000rpms, when it warms up it idles up to roughly 1500rpms. It use to not do it until the battery died and I put a new one in it. Ive pulled the IAC and cleaned it which got rid of a bouncing idle issue I had but It still idles at 1500 rpms after warm up. When put into gear it idles at 1000rpms and of course I got keep a firm hold on the brake pedal. Now Ive found if I disconnect the TPS it will idle at 1000rpms and in gear at around 600rpms just doesnt have alot of power. Ive replaced the TPS with same results. So Any Ideas Guys????

Khawk2

My 97 ZJ 4.0 at 159,000 miles was not starting well and one of the things I found was an erratic TPS, if I "wiggled" the TPS connector the idle increased or decreased. I replaced the TPS sensor with a dealer supplied part and still had the problem. I purchased a replacement connector kit from Auto Zone and installed with no change. I purchased another TPS from Auto Zone and the problem was solved. On the age vehicle you have and for the cost involved I would recommend replacing both and that may solve your problem. At the age of your vehicle it will be a good investment.

Good Luck.

Khawk2

Michael Luce

Well I have already replaced the TPS with one from Autozone, and the connector looks good. Now I did notice Autozone had 2 different Duralast TPS. A TPS324 and a TPS318, could this have anything to do with it? Both come with Limited Lifetime Warranty so its not a different warranty part and the price differs $13.00. Should I try the other part number? I mean I dont want to constantly replace this part especially if I dont know if the other one is bad.

QUESTION??? (For Testing Purposes) If I were to say disconnect the TPS from the intake and it idles fine due to not having that pressure on it from the plate. Would that mean bad TPS since its nonadjustment?????

caged

yeah, its probably still the tps. maybe exchange for other part number.

try shifting from 1st up through the gears to see if you get full power.

you can also pull and clean the IAC step up motor. clean with brake fluid and a scotch brite pad.

Khawk2

You don't say which part you installed but, I used the Auto Zone TPS324 Sensor and Auto Zone pigtail kit 1060 for the connector. By the way, the "pigtail" kit was packaged in two plastic bags, the outer one was an Auto Zone bag and the inside bag was a Mopar OEM part bag, just saying.

Just make sure your throttle body is clean so the throttle plate and shaft are free to move and the idle air control and passages are clean. Also you may want to check the idle air control motor to see if it is operating correctly. The IAC motor is a stepper motor and if that fails your idle will not be correct.

I mentioned in my eariler post that I had purchased a TPS from the Jeep dealer, they charged $120.00 for the part and it was defective, even after changing the connector the idle fluctuated when I wiggled the connector. I installed the Auto Zone TPS and the problem was gone.

Hang in there and continue to diasgnose and you will solve the problem, just don't get discouraged.

Michael Luce

I dont understand how there can be so many defective TPS out there. Ive read different forum of others having the same problem with getting defective TPS. Is there not a way to exchange these yet?

Thanks Khawk2

Khawk2

You did not say in your posts if you changed the TPS connector. I found on my Jeep that the connector as well as the TPS was the problem. As I recall the connector kit was about $35. I suggest you try that if you have not already.

As for defective parts the dealer posts a notice that there is no return on electrical parts. I suspect if you were a shop and purchasing a lot of parts they would make an exception but it seems the small guy is out of luck.

When I had a oil pressure indicator problem I purchased two different aftermarket sensors and even though they were ordered by make, year, model and engine size they did not work. The Jeep part solved the problem, it turns out there is some internal circuitry in the Jeep sender that was not in the aftermarket part.

Myself, in my experience, I will try an Auto Zone part before a dealer part because it seems that the quality is comparable and even if you finally have to go to the dealer for parts, when it's all said and done it will probably still be cheaper than a dealer repair.

Good Luck

dave1123

This is just my opinion and should be taken as such, BUT with electronic parts and sensors, Mopar takes the prize every time because they insure quality of materials and construction that are just not there in aftermarket parts. Take your oil pressure sender for instance. On my WJ, there is a piezoelectric crystal in it that changes conductivity with pressure. I tried 2 different Napa sensors that both didn't work right. The Mopar one did. Napa $47 TWICE! Mopar $73 done.

Khawk2

The opinion I expressed in my earlier post was confusing. I agree with dave1123. There are some components, especially electronics that are specifically designed and engineered for each vehicle. I had the same exact experience as d1123 with an oil pressure sender problem. The OEM part solved the problem after trying two aftermarket senders. There are many aftermarket parts that provide good serviceability but if in doubt, use OEM parts. No one wants to be a parts changer and while most of us enjoy working on our vehicles, the one thing that we cannot replace is lost time chasing a problem that a correct part would fix the first time.

If in doubt, use OEM parts. Sorry for any confusion.

dave1123

Not a problem, Khawk2! I was just spouting off about wasting time and $$$ putting a "new" part in only to have it NOT work and figuring that was NOT the problem when it MIGHT have been! One of the things I've come across about the oil pressure sensors is during the 2002-2003 changeover, it stopped being a pressure sensor and became a slide switch that doesn't read actually pressure! In other words, the gauge becomes an idiot light! It just reads 40 psi whenever the engine is running. It seems the reason for this is because the PCM doesn't need the information, so why use and expensive part just to keep the driver happy. The salesman I spoke to said they decided not to remove the gauge because it might cut sales if it didn't have one. It makes me wonder what other changes they made without telling us!

The whole point of this tirade is if you have a newer WJ that has a gauge, buy a sensor from Mopar for a 2000-2001.

Michael Luce

I finally figured it out!!!!!!! After all that trouble, hard to start, high idle in park and low idle in gear, misfiring and gas consumption, It turned out to be the MAP Sensor. I tested it I got 5v going into it but I was only getting like 1-2v coming out of it. I replaced it and all my problems went away like that and ran like new

Khawk2

Thanks for the update. Not only is it satisfying to fix the problem, by sharing the information it may help others.

Michael Luce

ya no problem, not many people do reply back with their fixes which makes it harder for me when looking for the problem

When testing you can remove the plug and check for your 5v DC wire as reference, and then plug it back in. The middle wire is going to be your output to the PCM which should read 5v DC as well with the KEY ON and ENGINE OFF. The opposite wire of your reference wire or input wire is going to be your ground. Now I dont know the correct measurement but as vacuum is increased that 5v will decrease to 1v as it gets to I think it is 18pounds of pressure. (Dont quote me 100%)
But in my case I wasnt even getting that 5v on that output wire