Hey Guys,
I'm new to the site,and would appreciate some advice.My son has his grandfathers 94 Pick up with 60k miles.
Before we gave it to him a year and and a half ago.Put a new distributor,wires,cap and plugs. She ran pretty well,but always had what felt like a miss.
Not being a mechanic,we took it to one.They changed the fuel filter,it ran a little better but never fixed.A year later and it seems to be getting worse.So far he has changed the plugs,
Cleaned the mass air flow sensor,and checked the throttle position sensor. He says the engine runs better with the TPS unplugged. Which I didn't think sounded right.to me.
We got a fuel gauge to test the fuel pressure,Instead of I believe 32lbs it was 80 lbs he also says he gets getting a code 24.
Does anyone have any idea what may be causing his problems,beside the nut behind the wheel.

Thanks in Advance
Pat

 

Has anybody done a compression test?

 

Code 24 is intake air temperature sensor signal. The IAT sensor is in the VAFM (what you referred to as MAF sensor), that could cause the rough running. How was it cleaned?

What engine is it? The is a lot of info on this forum regarding testing the VAFM, or if we know what engine, I can provide a link to the procedure.

Also, fuel pressure regulator return line blocked or valve stuck closed?

Welcome to YotaTech!

 

Welcome to YotaTech.

80psi is WAY too high; here's the spec: http://web.archive.org/web/201501160...28fuelpump.pdf I'm surprised you don't also have code 26 (Rich malfunction), but I'm not surprised it's running poorly.

A failed FPR could easily do that, but as AZ4runner suggests, I would first check the fuel return line. Just replace the line (at the FPR) with a 6mm (1/4") clear vinyl tubing to a suitable container. Use the jumper to run the fuel pump without starting the engine, then repeat the fuel pressure test. (While you're at it, you should get about 1/2 liter/min out of the return line.) If the fuel pressure drops back into spec, you probably have a blockage downstream in the return line.

 

First thanks for the response No he did not do a compression test, I will run one though,would you do the compression first or the other suggestions below first?

 

I would check/adjust valve lash before doing compression test.

 

[QUOTE=az4x4runner;52413251]Code 24 is intake air temperature sensor signal. The IAT sensor is in the VAFM (what you referred to as MAF sensor), that could cause the rough running. How was it cleaned?

Hi az 4X4 runner thanks for the reply,
My son said he made a mistake it is coming up code 25,also he said he used MAF sensor cleaner

What engine is it? The is a lot of info on this forum regarding testing the VAFM, or if we know what engine, I can provide a link to the procedure.
he has a 22re

"Also, fuel pressure regulator return line blocked or valve stuck closed?"

This was mentioned several times,I will hopefully be checking that tomorrow after work.

Welcome to YotaTech![/QUOTE
Thank You

Hi az 4X4 runner thanks for the reply,
My son said he made a mistake it is coming up code 25,

 

Millball
Thanks for the response
This site is awesome!!
Does the Code 25 change anything as far as the above suggestions.

Thanks Again

 

Code 25 is a lean condition. The FSM lists some possible causes. A large vacuum leak is another possible cause, as air is drawn in that is not metered so the fuel mixture will be incorrect (lean).

 

Diagnose the codes first, then check/adjust valve lash then do a compression test.

 

Typically I would say fix the codes first, but that fuel pressure needs nailed down to something better than "I think".

Re-run the pressure test, get a solid number.
If it's not to specifications run the flow test and check the pressure again as scope suggested.

24 year old vehicle with about 60k miles I would expect has seen some fuel gel issues. You may need to blow out fuel lines, service the injectors, put a clean fuel pump on it, and/clean and replace the tank.

PS, get a factory service manual. MAF cleaner should not be used on a VAFM, it will at best do nothing and could do bad things to it.