Backfires at 4k

DREWS94 · Nov 12, 2017

94 ranger that I recently put a 5.0 and auto into from an 89 mark 7.The truck runs great other then will not go above 4k rpm and it hits a wall.I have checked or installed items trying to chase it down. Distributor, harmonic balancer, fuel regulator, computer, coil, plugs, wires, changed fuel. I checked for air leaks or vacuum leaks while my son held at 35-37 rpm and I noticed the headers glowing big time. I believe to be ignition related but stuck an frusteraded after I keep checking things.

alwaysFlOoReD · Nov 12, 2017

AFAIK backfires are caused by a lean condition. Have you checked that you have enough fuel pressure [and volume] while this is happening?

lvwill · Nov 12, 2017

If the headers are glowing like that can pretty much guarantee you have a serious lean condition going on.
Stock 5.0 H.O. engines usually run way rich. Check for any codes and check fuel pressure.

DREWS94 · Nov 12, 2017

Yes that is why I replaced regulator and drove with the gauge on windshield.The plugs were not white and I can smell fuel sometimes I think it might be on the rich side maybe.

DREWS94 · Nov 12, 2017

Could the injectors be clogged?The motor had set for awhile but I have put cleaner through them

Skirbykat · Nov 12, 2017

I've seen similar symptoms caused by faulty MAF meter in Mustang GT before. Don't want you to throw money at parts, but certainly a possibility. Jives with the "lean condition" theory.

Sent from my XT1585 using Tapatalk

lvwill · Nov 12, 2017

That's a good possibility. Like I said before 5.0,s almost always run way rich. The headers glowing is not normal and points to a very lean condition.
What computer are you running?

DREWS94 · Nov 12, 2017

No maf and I am running the stock Lincoln computer

lvwill · Nov 12, 2017

Check the tps on the throttle body should be around .98 volts at idle and sweep smoothly to 4-5 volts at WOT. There is an article on this in the tech section. Also check the injectors, sitting with this crappy gas we have these days will destroy them.

DREWS94 · Nov 12, 2017

Will do. Already adjusted tps , is there a good way to test injectors

alwaysFlOoReD · Nov 12, 2017

Did you change fuel filter? You don't mention that. Also have you tested fuel pressure? I believe it should be at ~40psi. It's easy to leave it connected while running the engine, just use tape or tie wire to get it in a position that you can read it while test running. See if the pressure drops at your problem rpm.

DREWS94 · Nov 12, 2017

Yes I changed fuel filter and tested pressure, it was a little low but replaced regulator and was good.

lvwill · Nov 13, 2017

Do a quick search on YouTube for DIY fuel injector cleaning there are quite a few videos.

Is the truck doing this when you are driving or stationary in park ? The computer has a rev limiter that's right around that RPM when in park or neutral.

lvwill · Nov 14, 2017

OK I'm going to eat a little crow here lol.
Last night I went to my storage unit to get my mustang that is the donor for the b2. Last year I completely rebuilt the engine and put it back in the car to make sure all is good before doing the swap. It's been in the hot storage unit all summer here in Vegas and hasn't been started in 6 months or so. So it finally started and running like crap. Get it the 6 miles home when I opened the hood to check it out number 3 and 5 tubes were glowing a little. Today pulled the plugs and they were black as black gets. Pulled the injectors and those 2 were not closing, basically just dumping fuel in those 2 cylinders.

I hope this helps.

DREWS94 · Nov 14, 2017

No codes, exploring in to circuit 199 pin 39 off top of my head . If fuel injectors were leaking I don't think it would run as good as it does down low. It literally is like a switch is being flipped

Backfires at 4k

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