87 4.9 Running lean - help
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Joined: May 2004
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87 4.9 Running lean - help
I have recently inherited a troublesome truck. I have a 87 150 with a 4.9 and 4 speed manual. The truck was running horrible, I would have to hold the gas pedal down for a couple of minutes for the engine to warm up before it would idle, and even then it did not idle well. I ran both the KOEO and KOER tests and found a slew of codes. After consulting Hanes manual, this forum, and other web resources about the codes I replaced the EGR, EVR, EVP, MAP, TPS, IAB, HEGO, and the ECT as well as a general tune up. All of those related codes went away, I am now left with code 67(neutral safety circuit failure) in KOEO and codes 12 (cannot control high RPM), 25 (No knock), and 41 (HEGO detects system lean) in the KOER test. The truck still needs to be warmed up and it idles better, but still does not run well. What else could cause the engine to run lean? I have also just noticed a small exhaust leak at the manifold, could this be part of the reason the HEGO is reading lean? Any other reasons why the engine could be running lean?
Thanks
Thanks
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Joined: Nov 2004
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Trent, exhaust leak, vaccum leak, low fuel pressure, restricted injector or injectors, map/baro, tps, or faulty pcm or calibration all could cause a lean condition. You could also have a bad 02 that is just sending a lean signal to the pcm when in fact the engine is not lean but you say you replaced this.
Do a quick check of fuel pressure, but i think you will find a vaccum leak, expecially being how the dtc 12 is setting. You can either listen and check the obvious sources for a vaccum leak or start spraying carb cleaner around the intake area and see if you can pinpoint the leak by making the engine stumble. Fyi, carfull with the carb cleaner idea around hot exhaust manifolds or sources of open ignition.
Hope that gives you a starting point.
Do a quick check of fuel pressure, but i think you will find a vaccum leak, expecially being how the dtc 12 is setting. You can either listen and check the obvious sources for a vaccum leak or start spraying carb cleaner around the intake area and see if you can pinpoint the leak by making the engine stumble. Fyi, carfull with the carb cleaner idea around hot exhaust manifolds or sources of open ignition.
Hope that gives you a starting point.
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