2.3L ('83-'97) Stumbles and dies on cold start and after sitting.

[Ranger_97]

So I have been at this issue for a while now and still no luck. I have a ‘97 2.3L ranger 5-speed manual xlt

I went on a work trip and left my truck sitting perfectly fine and running per usual for two weeks. When I returned it was now firing up just fine, cranked normally and started but then after the high rev it would start to crawl back to idle but never catch itself and just die out. Start after start to no avail. If I give it some gas and save it on the down swing I can hold it steady or flutter it to hold it alive until it gets up to temp and can hold itself at idle again. After it gets warm it will sit at idle just fine and run like normal with no loss in power noticeably, no hiccups, no stalls. After a few days I did some scan testing and tried to troubleshoot. I was getting very negative short term trims and then started shooting all over the place. Got some MAF and o2 codes so I decided to replace the MAF with a walker products one from rock auto and the light has been off now since then but the truck is no better. I decided it was either fuel delivery or air mixture so I started to tackle those parts. I have replaced the IAC, ECT, Fuel pump, fuel filter, spark plugs and wires for fun, cleaned the throttle body and new air filter. It runs the same when I disconnect the MAF. I tested the FPR and it’s working when I pull the vacuum hose off the idle drops a bit and then back to steady when connected and no fuel in the line so haven’t replaced that yet. Looking for other suggestions on what could be the issue, hate revving the truck on cold start and don’t wanna murder the pistons anything too serious.

 

[SenorNoob]

Sounds like it's starving for fuel at startup.

Have you tried cycling the key a few times before you try to start it?

 

[Ranger_97]

Sounds like it's starving for fuel at startup.

Have you tried cycling the key a few times before you try to start it?

The o2 sensor is reading rich so I thought it was an air problem at first.

And yes I’ve tried to cycle and prime the system a few times before start and still no better. I tested the fuel pressure before I replaced the pump and I was getting 0psi key on engine off, 30psi on idle, and fast drop to 0psi when engine turned off so I suspected the pump because the regulator tested fine with the pressure gauge, dropped 10psi and shot back up when reconnected.

I don’t own a gauge so I tried to do a test after I replaced the pump at an auto parts store and I was able to start and drive but was still reading 0psi key in engine off and 0psi at idle so I just assumed the gauge was garbage and took off.

 

[SenorNoob]

Sounds like a massive leak. Injector stuck open maybe? Fuel leaking into the engine could cause no pressure on rail but still run VERY rich. I'd expect the exhaust to be unbearable at that point...

 

[Ranger_97]

Sounds like a massive leak. Injector stuck open maybe? Fuel leaking into the engine could cause no pressure on rail but still run VERY rich. I'd expect the exhaust to be unbearable at that point...

Surprisingly there is no dark smoke from the exhaust and not a very strong fuel smell from the tail pipe either. Going to look into injectors next and see what I can find with those. At least ford made it easy to check the injectors lol…. I wish.

 

[Ranger_97]

So I test the fuel injectors and they all tested good ohms and volts. Put the truck in clear flooded engine mode while
Both warm and cold and does not fire which is good, means my injectors should not be leaking if I understood that correctly. Still very stuck on this issue and not sure where to go from here. I don’t want to replace my O2 sensors because that wouldn’t affect my idling at cold start since they only read about a certain temp but the only codes I’m getting right now are rich O2 codes. Any suggestions are very much appreciated!

 

[TacoBelleGirl]

0psi when engine turned off so I suspected the pump because the regulator tested fine with the pressure gauge, dropped 10psi and shot back up when reconnected.

Where were you getting this reading from? Fuel pressure should still be kept even after key off so it sounds like it is very quickly escaping.
From my understanding there should really only be 3 places for the fuel pressure to escape (ignoring external leaks).
- Into an injector that's sticking open.
- Into the tank via the return line to due a failed FPR.
- Back into the tank via the feed. Defective pump or maybe a cracked line inside the tank?

I don’t want to replace my O2 sensors because that wouldn’t affect my idling at cold start

Someone with more experience than me can chime in if I am wrong, but a leaking fuel injector and a leaking FPR could both cause rich running conditions.

Do you have a code scanner that can show the 02 trims & ideally live data (with a graph)?
Knowing what the trims do based on RPMs and load can be a useful indication as to where the problem may be..

Also being able to see the reading can show if the sensor itself is bad or not.
If the sensor reading is pegged at it's highest or lowest value then it's probably a bad sensor or connector, but if it's readings are fluctuating and responding to what the car is doing then I wouldn't even consider replacing it until you sort out the other issues.

You are correct that the sensor itself shouldn't effect the truck's ability to start though, those come into play once it's started and warmed up a little bit.