Backfire at WOT

[TrAb]

Also... after confirming adequate fuel delivery, make sure the TPS is adjusted correctly... and test it to make sure it doesn't have a dead spot at WOT.

You DID put a good fuel pump, hotwire kit and fuel filter on it, right ? Adjustable FP regulator too ?

No i havent put on a hotwire kit yet but i have it waiting to go on, The car has a adjustable FPR that came on the car when i got it but i have not touched it. Fuel filter was replaced about 3 weeks ago, and the previous owner gave me a receipt where the FP was replaced a couple months ago. But it doesnt say what kind they put in.

 

[TrAb]

OK.... a few comments..





What is 'fine'? The only way to check the fuel pressure is to be driving the car while you can see a fp gage... the fp MUST rise 1 psi per 1 psi boost... as the pump gets weak, fp will start to rise as boost comes up, then start DROPPING as boost (and thus fuel demand) increases. This, of course, causes a lean condition/power loss/backfire/blown headgasket. VERY common problem. Just noting the base/line off pressure verifies nothing. So, say 43 psi base fp and 18 psi boost, wot fuel pressure should read 43+18= 61 psi. Adjust numbers to your conditions...



When the CEL blinks very quickly, it generally indicates a problem with the ecm or bad connection with the chip..



The car bogging at wot, and picking back up if you let off the gas a hair is very often indicative of insufficient fuel pressure/fuel pump going weak. If you haven't verified with your own eyes that the fp is increasing in a 1:1 ratio with boost, you are risking near certain catastrophic disaster. I wouldn't floor the gas again until I had a fp gage hooked up.... just get an extension hose and tape the gage to the windshield for testing purposes. VERY NEXT thing you should do if you haven't already... :wink:

Yeah the CEL stopped blinking, so thats a good sign i would think. Yes your right i did just check the base FP. Do you know where i can find a FP guage that i can view from inside the car locally? Would autozone or advaced have something like that?

 

[yullose]

Judging by many of your responses, you appear to be very "haphazard" and reckless with your shotgun approach to fixing things.
Flipflopping module wires and guessing about fuel supply details is a reckless recipe for disaster.

You need to slow down and do things/check things carefully, one at a time, being very methodical in your troubleshooting... or the car will bite you in the a$$ again quicker than you can say "Oh FVCK!"

Small injectors...
Fed by a (possibly) stock fuel pump...
Powered by the factory wiring harness...
Unconfirmed WOT fuel pressure...
Unchecked fuel filter...


You will be putting headgaskets on it soon.

The hotwire harness will mean the difference between 9 volts and 14 volts at the pump.
That is the first thing I'd get on the car before going any further.

 

[TrAb]

Judging by many of your responses, you appear to be very "haphazard" and reckless with your shotgun approach to fixing things.
Flipflopping module wires and guessing about fuel supply details is a reckless recipe for disaster.

You need to slow down and do things/check things carefully, one at a time, being very methodical in your troubleshooting... or the car will bite you in the a$$ again quicker than you can say "Oh FVCK!"

Small injectors...
Fed by a (possibly) stock fuel pump...
Powered by the factory wiring harness...
Unconfirmed WOT fuel pressure...
Unchecked fuel filter...


You will be putting headgaskets on it soon.

The hotwire harness will mean the difference between 9 volts and 14 volts at the pump.
That is the first thing I'd get on the car before going any further.

Well the module wires, that wasnt really guess work. As i stated the wierd ignition module i got from autozone, it came with intructions showing two different wiring methods. It says try both, so i did???

But yeah, trust me im going to install the Hotwire Fp kit this friday. The fuel filter is new i know this and so is the fuel pump. But im trying to find a FP guage locally today so i can get it straightened out asap.

 

[yullose]

The fuel filter is new i know this and so is the fuel pump. But im trying to find a FP guage locally today so i can get it straightened out asap.

If you didn't put the filter or pump in yourself, don't assume they are good or quality parts. They very well may be fine, but these cars are not very forgiving with assumptions. You may have gotten a crappy load of gas and now the filter is plugged... it may have sat with bad fuel in the tank, etc...

Do it right and drop the tank, inspect/replace the pump with a KNOWN good pump, replace the filter yourself and install the hotwire kit.

This way you KNOW for sure it's good and working.

How do you know the previous owner didn't put a Chinese made piece of crap Autozone fuel pump in the tank ?
Unless you look at it yourself, you will never know... and you could be chasing gremlins all season, or at least until you spit out a head gasket. :wink:

 

[TrAb]

Yeah your right about the parts, previous owner was taking it to some shop down in FL. So they probably were putting on the cheapest parts possible. Im picking up a FP guage today after work to check everything out and make sure the FP is right. Ill install that hotwire kit before i take the car our again though. I just want to make the car right, i am not going to be beating on this car for the most part. Just going to take it easy on it and drive it like it was a kia ...

 

[bmackinnon]

Im picking up a FP guage today after work to check everything out and make sure the FP is right. Ill install that hotwire kit before i take the car our again though. I just want to make the car right, i am not going to be beating on this car for the most part. Just going to take it easy on it and drive it like it was a kia ...

THERE ya' go!! Good plan! Let us know the fp test results... and if you see the fp dropping, let off the gas immediately! These cars are awesome once you get 'em right... and easy to diagnose once you're familiar with all their little peculiarities... you'll get it!! :biggrin:

 

[TrAb]

I picked one up at autozone, i think the line should be long enough. Dang thing was almost $50 . Guy at the counter told me i could use my compression tester, but i heard that it will just tear them up...

 

[TrAb]

Aight guys, i got home and hooked up the FP tester. I am only getting around 34-35psi while the car is idle'ing. Is that normal? I havent got to test it while driving. Wanted to see if that was to low, of course when i pull the vaccum line off it goes to around 42-43psi.

 

[bmackinnon]

Aight guys, i got home and hooked up the FP tester. I am only getting around 34-35psi while the car is idle'ing. Is that normal? I havent got to test it while driving. Wanted to see if that was to low, of course when i pull the vaccum line off it goes to around 42-43psi.

Yep, that's right.... vacuum on the fpr drops the pressure and boost raises the pressure... so while the car is idleing, it's pulling a vac on the reg, dropping the pressure... its about 1 psi fp (drop) per 2" hg vac... so at say 16 in. hg vac (about normal for a stockish setup) the fp will drop ~ 8 psi.... about what you have.... now we need to see if the fp is rising with boost.... makes sense, right? at 0 vac/0 psi boost (same as pulling the line off the reg) you get base pressure... and as boost rises, the fp rises above the base... run it up to ~15 psi boost and see if you get a solid 43+15=58 psi fp....