dracon79 Posted October 24, 2007 Posted October 24, 2007 I have an 88 jeep comanche with the 4.0 in it. When I first start the truck after it has been sitting a while like over night, you go to hit the gas and the rpms drop and almost dies and sometimes does die. But as soon as you let it warm up that goes away. Also at high speeds with a load like going up a hill on the highway it starts to buck a little like its not getting enough fuel. I'm thinking maybe fuel pump? I replaced the tps and stepper motor and o2 sensor no change.
FxRacing282 Posted October 24, 2007 Posted October 24, 2007 air filter or bad compression most likely
dracon79 Posted October 24, 2007 Author Posted October 24, 2007 I don't think it could be bad compression it doesnt use any oil and it takes forever before the oil even changes color.
FxRacing282 Posted October 24, 2007 Posted October 24, 2007 its possible, check your air filter. check plugs. run the tank empty or close to and put some new stuff in
carnuck Posted October 24, 2007 Posted October 24, 2007 try the gas filter and cleaning the throttle body. CTS may be shot too. (coolant sensor for the EFI)
Eagle Posted October 24, 2007 Posted October 24, 2007 EGR maybe? Also, make certain that the throttle body is tight on the manifold. A small leak at the mounting flange might cause behavior sort of like that, and as the engine warms up the aluminum would expand to make a better seal.
jtdesigns Posted October 24, 2007 Posted October 24, 2007 EGR maybe? Also, make certain that the throttle body is tight on the manifold. A small leak at the mounting flange might cause behavior sort of like that, and as the engine warms up the aluminum would expand to make a better seal. Wouldn't a leak on the TB cause a raised idle? Sounds plausible with it getting warm and closing the gap though,
FxRacing282 Posted October 24, 2007 Posted October 24, 2007 then how do you explain no power with loads if the aluminum has sealed?
jtdesigns Posted October 24, 2007 Posted October 24, 2007 then how do you explain no power with loads if the aluminum has sealed? Could be more than one problem,,, How would you check the egr value?
FxRacing282 Posted October 24, 2007 Posted October 24, 2007 see if you can smell exhaust near the TB. if you have to much exhuast going in, in most cases there is a crappy idle and stalling, but noticeable at higher RPM's
dracon79 Posted November 2, 2007 Author Posted November 2, 2007 I replaced the egr with a brand new one and it is still doing the same thing even put in a new fuel pump can't figure this one out. I checked the egr solenoid and it seems good has vac and power. CTS,fuel pump, air filter, is also been replaced. TB is tightly secured. can't seem to figure this one out. :???:
HOrnbrod Posted November 2, 2007 Posted November 2, 2007 Is it running hot at all? Check for a clogged cat.
FxRacing282 Posted November 2, 2007 Posted November 2, 2007 did you check your plugs? Go to the nearest vocational school and have them run a diagnosis on your ecu mod.
dracon79 Posted November 3, 2007 Author Posted November 3, 2007 Ok I got a vaccum pump tester and did the tests that are on this page to the egr solenoid. http://www.lunghd.com/Tech_Articles/Eng ... ostics.htm As he states in the test that when the connector is plugged in and engine hot there should be vaccum but there is not I tried there is only vaccum when I unplug the connector. I used a voltmeter to test the connector and as far as I can tell it always gets juice. So I am not sure if this is a solenoid issue or a engine computer issue.
FxRacing282 Posted November 3, 2007 Posted November 3, 2007 have you tried driving with you EGR blocked? my truck has a blocked EGR and its great, from what people tell me, they can add some power as the air is not as warm going into the cylinder. Per haps you need to check your fuel filter or filters, i don't know much about TBI systems but i suspect that there is a fuel filter in the TB, try looking for one and if you find it inspect and replace if necessary, check for an inline and a tank filter also.
Eagle Posted November 3, 2007 Posted November 3, 2007 It may be one (or more) partially clogged injectors. When the engine is cold, it does not respond to sensor inputs. During warmup, it runs in "open loop" mode, which means it ignores the sensors and runs on a pre-mapped fuel curve that's built into the ECU. With the '88 XJ, I have owned it for so long that in the winter I can feel when it switches. It's about 2 miles down the road, on a level area where I run at neutral throttle. Right in that area on cold morings I usually feel a slight jump and after that the throttle response changes subtley. Once the sensors cut in and the O2 sensor starts reporting the mixture to the ECU, the ECU can compensate (to the extent the injectors have enough capacity -- which they would at idle) for clogging, but the pre-mapped fuel curve would have no way to compensate for this condition.
dracon79 Posted November 5, 2007 Author Posted November 5, 2007 Well I replaced the cps that didn't work either. I replaced the fuel filter no good either. I try checking the ecu and cat. Going to check the tps again with my voltmeter but I replaced that just months ago so I don't think that could be it. So weird that it only does this when its cold once it warms up no problems.
FxRacing282 Posted November 5, 2007 Posted November 5, 2007 maybe your rings are starting to wear a little bit. or perhaps the cold chevy v8 problem is wearing off into your jeep
dracon79 Posted November 5, 2007 Author Posted November 5, 2007 Ok Ill check the injectors I recently replaced the two injectors closest to the radiator because they were leaking. So Ill take a look at the others. thanks
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