darren509

Here are what my plugs all look like.

darren509

Also I was checking voltage at the iac connector while running and one of the pins has 13 volts. Is that correct ? Rechecked the fuel pressure and I have 44 koeo and 48 steady while running. I noticed it definitely has a miss to it that can be felt below 2000 rpm and gets worse the higher the rpm. Performed a a vacuum gauge reading and It goes to almost 15hg and bounces down to as low as 12hg. its a slow bounce and every now and then it drops to 12 and then back up. I followed some vacuum lines that appear to go under the battery tray and maybe inside the bumper. I sprayed starting fluid all over the lines that are connected right behind the drivers head light but no change in idle was found.

darren509

I will attempt to put in a link of my fuel pressure test, vacuum and then idle. I tested the TPS today with an analog meter and it seems perfect. Fuel pressure and idle This one is the vacuum

Phil96zj

Did you find out what it was?

darren509

Not yet. I haven't had time to touch in in the last few days. A new ecm was ordered because my friend who owns it is dead set on that being the problem. I think it's something else.

NW jeepin

i'm having a similar problem on my 96 xj and just changed out the ecu tonight and it still dose the same thing... hopefully you have better luck

97grand4.0

Cycle the key on and off about 4 times, maybe 3 maybe 5, and leave it ON the last time. You should get the chekc engine light flashing codes.
You mention your voltage being 13 and dropping to 12.5 when goosing it, that's not right. Should be steady or if anything increasing slightly. Take it to Advance and have them put the free test on it. It's free.

darren509

Thank you for yu reply. However taking it to auto zone will not yield any results as you cannot read the computer while the car is running

97grand4.0

No, you misunderstand. Have them test the charging and starting system. Your voltage sounds too low and is acting strange when you increase idle speed. That and the other problems suggest to me a shorted diode in the alt. They can print out the diode pattern and regulator function, and also view it on the LED screen.
Let me know how the key test works to see the ECM codes.

darren509

Ok I get you now. I'm not sure it will drive that far though. She bucks and cuts out pretty bad. I gave tried the key code test before and it does not seem to work. 8 have read it is a common issue with 98 models to not work with the key.

97grand4.0

Never heard of the 'key trick' not working, so the ecm is still in play here, along with the scanners not working.

Aside from that you really need some more tools in your war chest. Go to the boneyard and scalp a MAP, TPS, and IAC motor used about $4 ea. Then take the whole throttle body off, four 1/2" bolts on top of the manifold. Much easier to change them out like that. In fact ..just pull it from the boneyard like that too. Too expensive to throw new parts at it.

darren509

I read dozens of posts on forums about the key trick not working on 98 models. After the ecm gets here I'll know for sure

97grand4.0

Come to think about it, I do seem to recall that some had the 97 style ecm that it worked on, and others did not, so yeah maybe the key trick dont work.

97grand4.0

Have you ruled out jumped timing? Have seen a few chains and gears that were pretty munched, do you know how to check the chain wear, and have you looked at the distributor for horizontal bushing play at the rotor..also end play not excessive, and the gear where it meets the cam can wear to nothing if it's bad enough...this is an easy one...just wiggle the rotor...they say some of those are so bad that they reluctor thing clobbers the cam sensor when they spin. Check the timing with a light and see if it's all over the place.

darren509

Will do.