Momentary Idle Surge at Startup
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5th Wheeling
Joined: Jun 2017
Posts: 38
Likes: 8
Momentary Idle Surge at Startup
Hey guys!
I have a 1995 F150 4x4 with a 351 run on a 302 computer.
I've been running this setup for 5 years now with no problems until now. Wondering if any of you guys have experienced this:
When I start the truck, everything is fine until the ECU finally kicks in the adaptive maps. Suddenly, the idle will go up from 600 to 1500 rpm, and the CEL will blink 4 times. It sits at 1500 rpm anywhere from 5-30 seconds. It's different every time. Then it idles back down to 600 rpm and runs perfect after that. If I shift the truck into D or R before or during the surge, the engine immediately drops down to normal idle speed and is fine. After the CEL blinks, it turns off and doesn't turn back on. Could it be a sign of a weak or dying TPS? I vaguely remember having strange surging problems when my original TPS completely died.
My IAC and TPS are 5 years old. EGR is completely blocked off. I tried resetting and remapping the computer, but that made no change. I am going to check for stored codes if any and post them if I have anything relevant. The TPS and IAC are on a lifetime warranty so I could swap them out if anything. I had the ECU out 5 years ago and the board looked perfect then. No burst or bulging caps.
Other than that the truck runs great! I had just recently put new plugs in it, and it was absolutely lovely up to this point. What do you guys think?
I have a 1995 F150 4x4 with a 351 run on a 302 computer.
I've been running this setup for 5 years now with no problems until now. Wondering if any of you guys have experienced this:
When I start the truck, everything is fine until the ECU finally kicks in the adaptive maps. Suddenly, the idle will go up from 600 to 1500 rpm, and the CEL will blink 4 times. It sits at 1500 rpm anywhere from 5-30 seconds. It's different every time. Then it idles back down to 600 rpm and runs perfect after that. If I shift the truck into D or R before or during the surge, the engine immediately drops down to normal idle speed and is fine. After the CEL blinks, it turns off and doesn't turn back on. Could it be a sign of a weak or dying TPS? I vaguely remember having strange surging problems when my original TPS completely died.
My IAC and TPS are 5 years old. EGR is completely blocked off. I tried resetting and remapping the computer, but that made no change. I am going to check for stored codes if any and post them if I have anything relevant. The TPS and IAC are on a lifetime warranty so I could swap them out if anything. I had the ECU out 5 years ago and the board looked perfect then. No burst or bulging caps.
Other than that the truck runs great! I had just recently put new plugs in it, and it was absolutely lovely up to this point. What do you guys think?
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
You need to pull codes from the PCM and see if they are consistent or change from one set to another.
The capacitors may have looked well 5 years ago, but the capacitors are 24-25 years old, and may very well be leaking or failing.
Been there..done that.
The capacitors may have looked well 5 years ago, but the capacitors are 24-25 years old, and may very well be leaking or failing.
Been there..done that.
Elder User
Joined: Dec 2016
Posts: 854
Likes: 39
From: Mid Missouri
OP,
yes what you describe is exactly what mine did for about 6 months. I would check for codes every now and then and none ever came up other than the 10 and 111. The strange thing is one day about 3 months ago the surging at startup with blinking CEL stopped and hasn’t returned. I imagine someday the problem will return but what’s frustrating is the PCM never threw a code for it even though it blinked every morning on a cold startup so knowing where to start diagnosing was difficult.
Sorry I know my post wasn’t of any help, just wanted to share my experience. I always suspected the TPS for what’s it worth.
yes what you describe is exactly what mine did for about 6 months. I would check for codes every now and then and none ever came up other than the 10 and 111. The strange thing is one day about 3 months ago the surging at startup with blinking CEL stopped and hasn’t returned. I imagine someday the problem will return but what’s frustrating is the PCM never threw a code for it even though it blinked every morning on a cold startup so knowing where to start diagnosing was difficult.
Sorry I know my post wasn’t of any help, just wanted to share my experience. I always suspected the TPS for what’s it worth.
Thread Starter
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5th Wheeling
Joined: Jun 2017
Posts: 38
Likes: 8
OP,
yes what you describe is exactly what mine did for about 6 months. I would check for codes every now and then and none ever came up other than the 10 and 111. The strange thing is one day about 3 months ago the surging at startup with blinking CEL stopped and hasn’t returned. I imagine someday the problem will return but what’s frustrating is the PCM never threw a code for it even though it blinked every morning on a cold startup so knowing where to start diagnosing was difficult.
Sorry I know my post wasn’t of any help, just wanted to share my experience. I always suspected the TPS for what’s it worth.
yes what you describe is exactly what mine did for about 6 months. I would check for codes every now and then and none ever came up other than the 10 and 111. The strange thing is one day about 3 months ago the surging at startup with blinking CEL stopped and hasn’t returned. I imagine someday the problem will return but what’s frustrating is the PCM never threw a code for it even though it blinked every morning on a cold startup so knowing where to start diagnosing was difficult.
Sorry I know my post wasn’t of any help, just wanted to share my experience. I always suspected the TPS for what’s it worth.
For now, I might exchange my TPS for a new one to see if that makes any difference. If not, oh well! It's not harming anything else.
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