24 valve throttle problem

phale

phale

Comp Diesel Sponsor
Joined
Dec 12, 2006
Messages
935
We have a 99 24 valve in the shop that starts and idles normally, but anything over 3% throttle position the truck revs to the moon like it is calling for max fuel. The tps has been changed, we swapped out the crank sensor with no change. We have verified that we have a good signal going from the apps to the ecm and can watch the TPS go through a full swing from 0 to 100 with the correct corresponding voltages. What We don't have is a signal to the pump. I can watch the idle switch click off at the pump wiring harness connector but I cannot find any pins that have a varing voltage. Does anyone know which pin carries the rpm signal from the ecm to the pump?
 
I would say the TPS is adjusted out too far.... back the throttle stop in some, but mark where you started if this for some reason doesnt change it...
 
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I will try that, but the tps makes a full sweep from 0 to 100% when watching it on the scan tool. I get the proper voltage to signal that the truck is coming off idle, but I am not sure what kind of voltage I should be seeing to vary the throttle at the pump. I think it should be coming from the + side of the data link but am not sure and the wiring schematics don't say what the value or range of values should be. I believe that the issue is either the ECM or the pump but they are both too expensive to begin throwing parts at.
 
phale said:
I will try that, but the tps makes a full sweep from 0 to 100% when watching it on the scan tool. I get the proper voltage to signal that the truck is coming off idle, but I am not sure what kind of voltage I should be seeing to vary the throttle at the pump. I think it should be coming from the + side of the data link but am not sure and the wiring schematics don't say what the value or range of values should be. I believe that the issue is either the ECM or the pump but they are both too expensive to begin throwing parts at.
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I understand, but I messed around with trying to change idle with the throttle stops a while back.... and the one that the tps rests on at idle, I adjusted in out... or down to try and allow truck to idle lower, well the truck idled fine, but as soon as i came off idle it would spin to the moon.... so try adjusting it toward the arm like you are gonna idle the truck up per say.... but like I said mark where you start so you can go back if thats not the problem.... worth a try without throwing parts at it......it shouldnt take much, maybe a half to full turn or so max....if it starts idling the truck up its probably too far...do this with the truck off
 
Well it seems that the ECM may be the problem, all tests lead to it and it is killing the batteries if left overnight. Now the big question, is there anywhere that repairs/remans these ecms? I really don't want to give the mega bucks the dealer wants for a new one.
 
Auto Computer Exchange in Florida. Used to be if you bought from them off of ebay you got a lifetime warranty. Dunno anymore. I got one from them, and had it replaced 3 times, no charge. It wasn't their fault though. Turns out my alternator was bad, sending out ac current frying the ecm. New alternator, no problems since.
 
well when it rains it pours. Now we have two of them at the shop with the same symptoms. Only difference is that the second one only does it when it wants. Some times it runs fine others it does not.
 
Mine started out just doing it random, just a little blip here and there, then it got to where it was like it truck wasn't getting the tps signal. You could hold it at half throttle and it would be fine, then drop to no rpm, ya never knew what it was going to do. Good luck with them, I've seen quite a few trucks with the same symptoms and the ecm being bad. You're not the only one.
 
Make absolutely certain those internet jerks program the CORRECT VIN into the ECM before they send it to you. They didn't program mine and it puts up the check engine light and ABS light 100% of the time. If the VIN in the ECM and ABS don't match, everything will work, but the light stays on. Folks have argued with me before, but all I can tell you is once I had the VIN changed, the light went off. And most dealers CAN'T change a VIN. They can only put a VIN into a blank module...or so they say...so you'll buy one from them. Don't get ripped off! Careful. $.02
 
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