kataklysm01

I've got some weird stuff happening. The check engine light is on, the engine runs like I have some vacuum leak. I've checked all hoses, I had two leaks but didn't fix the issue. I replaced the IAC valve and O2 sensor so far. After a while if the light shuts off, it works pretty good. While the light is on under load and low rpm will give me lean backfires through TB.

I've sprayed brake cleaner around TB gasket without any difference.

The What'sUP malfunction codes window is not showing me anything wrong or the SES is not lighting up. It's the actual light under the dash that's lighting up.

Any guesses?

RBob

iTrader: (1)

With an error such as this, need to step back and take a look at the big picture. Need to use as many clues as possible.

Is the WUD still displaying correct data while the SES is on?

Is this a recent issue, or has it occurred in the past (even intermittently)?

Does the SES always do the 'blink' at key-on, engine-off? Check this each time you go to start the engine. SES turns on briefly, blinks off, then turns on solid. This is a sign that the ECM is running the actual firmware, and is not in limp mode.

Once the engine is running the SES should be off.

Have the injectors been swapped for larger ones, or, has the fuel pressure been increased. If so then limp mode will be richer, which is the opposite of the lean pop.

Check the EFI harness grounds on the back of the cylinder head(s). Check the battery cables to make sure that they are good and that the battery terminal clamps are tight.

Another item to check is the quad-driver chip in the ECM. The one that drives the SES also drives the EGR solenoid and the TCC lockup solenoid. Either of those can fry the q-drvr chip which can affect the SES.

It is U15 and is located near the EFI harness connectors. There are two q-drvr chips in the ECM. Both are 16 pin devices with the 4 center pins attached to larger copper areas (heat sinks).

See if there is any physical damage to the chip: craters, cranked, burnt, or even slightly off color from over heating.

RBob.

kataklysm01

Thanks for the reply. These type of phenomenon have been happening since October,mainly the engine suddenly needing an adjustment of the VE table of up to 15%. I had so far replaced fuel filter, checked fuel pressure, ran some Seafoam and injector cleaner in the fuel and in a vacuum line.

Here's an update for today; I retorqued the TB and adapter plate to the intake manifold. I checked the spark plugs and they were all perfectly off-white, no sign of oil or overly lean. Cylinder 1 (AMC 401) had a few white specs on it(fuel additives?), not the others. Compression for all 8 cyl was all in range from 170-180 psi.

Retorquing the intake, the rear of the intake bolts and some others were loose. So I torqued them and retightened with a wrench the ones I couldn't use the T-wrench. The jeep works much better. No missing and popping while driving, idle is better.

The SES light has shut off. I tried turning the jeep on and off and getting the light to flash, but it would just do like you said, On, pause and solid and it would stay on while the jeep ran, and the jeep ran like crap. I inspected the plugs for all sensors, no vacuum leaks that I can find. The brake booster holds vacuum.

I still have the TBI pop while driving at low speed, around 1000-1500 rpm and high MAP. It's worse when the engine is colder, and seems better after the engine has warmed up and run for a while. No stumbling that I could notice tonight when I drove to town at speeds of up to 50mph and while I was plowing in high range 1st gear. So power is there and the stumbling is gone.

So things are looking better. I'll have a better idea after I run it a bit more.

Thanks for the suggestions so far.