Engine Hot start and idle issues

92lx302

Member
Jul 18, 2021
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Indiana
I recently did some engine work to my 92 fox such as gt40p heads, 1.6 rockers, TFS1 cam, track heat intake, 70mm throttle body. Once I started it up it seemed to be running ok but once it warmed up it didn’t want to stay running. I started on some checks and tried pulling codes but it’s not really showing anything major. The idle seems a little weird as it will drop 300rpm or so and bounce back up. Also the engine sounds as if it is Revving higher than what the gauge is showing. The engine has a lot of new sensors and the distributor is new. Also I replaced a few burnt up capacitors on the computer. Looking for any ideas or leads.
 
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KRUISR

5 Year Member
Apr 16, 2015
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Base Idle Reset... also follow the Surging Idle Checklist

Make sure IAC is clean and fully functioning.
 
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92lx302

Member
Jul 18, 2021
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2
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33
Indiana
I did a idle reset and checked the TPS voltage and it is in range. The IAC is one of the sensors I haven’t replaced and is OEM. Would this also cause hot start problems? The car won’t start when it starts to warm up.
 

KRUISR

5 Year Member
Apr 16, 2015
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I think the key to the IAC is it needs to move freely. I just did a good cleaning (got a whole bunch of flaky chunks out) and it definitely works better. I don't know for sure if a clean/new IAC would improve hot starts. I think they would because any time I have an issue with a hot start I press the throttle a little and it starts right up (something a proper working IAC could/should take care of).
 

92lx302

Member
Jul 18, 2021
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Indiana
I’m gonna change the IAC or clean it like you suggested. I can start the car when it’s warm with the pedal to the floor but it won’t last long. It will either die right away or idle rough for a min and then die. It has a new ECT sensor, the old distributor or the new one doesn’t make a difference.
 

Rawdoggy

New Member
Jul 17, 2021
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Maine
Nope it shuts off after that initial prime.
Mines doing the same thing but it will start but it has a skip then when I go a little ways it dies on me. The battery was dead but I dont know if it would cause it to shut off like it was. I guess I'll have to register it because I'm gonna get tickets if I keep trying it out and it breaks down on side of the road
 

Rawdoggy

New Member
Jul 17, 2021
2
0
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40
Maine
Mines doing the same thing but it will start but it has a skip then when I go a little ways it dies on me. The battery was dead but I dont know if it would cause it to shut off like it was. I guess I'll have to register it because I'm gonna get tickets if I keep trying it out and it breaks down on side of the road
There is a vacuum line that came off somewhere. I would like to get it running right I have alot of time and money into it.im gonna hang on to it and try to get it right. It needs all the suspension parts u have to keep your foot on the gas to keep it running. I'm new to this so any help would be appreciated
 

92lx302

Member
Jul 18, 2021
8
2
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33
Indiana
I still haven’t figured mine out yet. It seems like I have grounding issues or something going on. My fan controller fuse recently started blowing. Seems like this all stemmed after I changed out my heater core. I don’t have a lot of time but weekends.
 

Boostedpimp

15 Year Member
May 8, 2003
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whats your timing? I have had that cam in a a few cars and it always seemed to be happier with more timing
 

92lx302

Member
Jul 18, 2021
8
2
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33
Indiana
Also I have pulled the codes and most common codes from deleted smog and egr. However I did get a 96 code which is a secondary fuel pump fault. I did change the fuel pump relay but that didn’t fix anything. I have a AFPR with a gauge and the fuel pressure is fine and doesn’t drop or dip when it gets warm.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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polk county florida
What is the fuel pressure when it dies? You two need to do the 'surging idle checklist
Read the intro, do not skip any steps, I know you don't have a 'surging idle' but it works for idle/stall problems.
@92lx302 you may have a pinched wire is the area you worked last, trace the fan controller wires.
@Rawdoggy check your charging system, if it is not charging enough or your battery is shorted (won't take a charge) it can shut down.
 

92lx302

Member
Jul 18, 2021
8
2
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33
Indiana
I’ve never heard that before about timing. 14-16 has always been the sweet spot for a few of the mildly modded 5 liters I’ve owned.