Efi stumble and backfire - mustang efi

[landshark]

I have been having an intermittent issue where the 76 will stumble then lack power and sometimes backfire through the exhaust. Happens allot when pulling away from a stop or slow rolling coast then giving throttle. Letting off and hitting the gas again sometimes "cures" it but seems to be getting worse. I check the timing last night and it was at 13 I took the timing back to 10 and doesn't seem any better.

I have been looking at posts on CB.com and my next thought was to check vacuum then check and clean the MAF And TPS.

I saw one post where it was a bad distributer but wanted to trouble shoot before I start guessing at replacement parts.

Any advice?

[Rox Crusher]

Have you checked to see if you have any codes ?

I used to have to clean my MAF every 6 months or so.

You are welcome to borrow an ECM and / or distributor if that would help.

[landshark]

I have steady 38 psi fuel pressure on idle and throttling it up when parked. 40psi when I shut off.

I have a steady 14hg of vacuum at idle about 17-19 with some throttle. Blipping the throttle it goes up to 20 or so.

I will see if I can put some kind of line together and make the fuel pressure gauge readable while driving.

Haven't pulled codes will do that tomorrow.

Let's see what I find with fuel pressure and codes and go from there. I have a sneaking suspicion I might have a vacuum leak somewhere. Maybe gaskets and/or plugs.

[kchaser]

I had backfire missing and stalling issues on my boosted 93 fox. Only happen from time to time without repeatability. Went to great lengths to not just throw parts at it but codes were little help so I replaced.... Plugs cap rotor, ignition switch, key switch, bypass Msd, removed program and chip, master ecu relay,TFI and finally the winner was a new distributor. Likely was the pip sensor. What a pain.

[Rox Crusher]

I have steady 38 psi fuel pressure on idle and throttling it up when parked. 40psi when I shut off.

I will see if I can put some kind of line together and make the fuel pressure gauge readable while driving.

That's what I really love about my new Dakota digital gauge set-up. I got the optional fuel pressure sensor which allows fuel pressure to be displayed on the gauge / dash.

I also retained tge fuel pressure gauge on the rail for visibility while under the hood.

[landshark]

I had backfire missing and stalling issues on my boosted 93 fox. Only happen from time to time without repeatability. Went to great lengths to not just throw parts at it but codes were little help so I replaced.... Plugs cap rotor, ignition switch, key switch, bypass Msd, removed program and chip, master ecu relay,TFI and finally the winner was a new distributor. Likely was the pip sensor. What a pain.

Iam wondering the same thing as others solved it by replacing the distributor . I might throw one on there and see if that solves it. Not sure where I got my distributor might have been a reman.

Will test fuel pressure while driving and recheck vacuum connections just to make sure. I've been down the throw parts at it path before and would like to avoid it.

[kchaser]

I picked the distributor up at NAPA with the TFI installed for under $100 I think.

[landshark]

Partial good news. Rerouted some of the vacuum lines, put a dedicated line to the c4 and it shifts much much better. I have great vacuum as well so I can move on to fuel pressure under load. Hope to pick up another gauge at harbor freight tomorrow.

[Jesus_man]

Could be TFI for intermittent issues. BTDT.

[landshark]

Put a electronic auto meter fuel pressure gauge on the rail. Getting 32-34 psi at idle. Romping the throttle will spike it to 38 or so. Light throttle cruising it hovers around 32 but drop a bit more coasting.

Seems low to me should be 38 pretty much all the time of not higher?

My next step is to check the voltage at the pump.

After that I assume drop the tank?

[landshark]

I cleaned the maf, Act and throttle body. Trimmed my throttle and kick down cable a bit as I never fine tuned it.

See if there's any difference tomorrow but Iam still dropping the tank and replacing the fuel pump with a aero motive stealth pump with a new filter, suspect I will find some crap in there.

Also pulled koeo codes but nothing came up besides the typical 80's EGR stuff.

[landshark]

Might jinx it but stumble is gone so far after I cleaned the MAF, ACT and throttle body. Didn't look dirty but guess it was.

[Gregg]

It made a difference when I cleaned the the MAF sensor on mine. What'd you use to clean the ACT...the same MAF sensor cleaner?

[landshark]

It made a difference when I cleaned the the MAF sensor on mine. What'd you use to clean the ACT...the same MAF sensor cleaner?

yes, used MAF cleaner on everything just sprayed the MAF sensor but didn't wipe it off or anything - wiped down everything else really good as well as the inside the air intake and TB.. so far so good.

[ZOSO]

With that being said in the mustang world I have seen guys have issues with oiled filters. The oil will collect on the maf wire and can cause a lean condition. I had a buddy back in 06ish lose an engine from it.

[landshark]

No oil on my filter using a dry one. So far so good no stumble in 3 days.

[Eck]

I might have to try to clean my MAF. I've been getting intermittent backfire between high 2nd and 3rd.

[EFI Guy]

I missed this thread, haven't been on in a while. Is it still running good now Chris?

[landshark]

So far so good. The MAF and ACT cleaning seemed to have solved it.

Good news is I have a nice new stealth fuel pump backup I can try out [emoji3]