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Problem finally solved! Turns out it was a bad ignition coil. I found a mechanic with a portable engine analyzer. We hooked it up and I went for a test drive. All 8 cylinders were breaking up. He suggested replacing the coil, which I did - with a Mallory. Runs great now. Thanks for all the...

Ok, now I'm stumped. Here's a recap: basically a stock efi 5.0. It runs fine under every condition, except when it hits about 3600 rpm under WOT. In other words, its fine at idle, partial acceleration all the way to redline, WOT up to 3600, cruise; all ok. Under WOT when it hits 3600, I get...

Ok. Thanks for all the help, Jrichker. I'll try the steps you've outlined. Buddy

My mistake, 28 is not a code, the fuel pressure was 28 with the key on, but engine off. There are no codes, either engine off or engine running. Fuel pressure at idle was 32 and fuel pressure with the vac. line disconnected was 41. Buddy

Seems to be about the same, hot or cold. This morning, it would pull strong for 1-2 seconds, then start popping, hesitating, etc. I checked the fuel pressure: KOEO: 28 idle: 32 vac. line disconnected: 41 I don't see any fuel in the vac line. If it's the fuel pump, what brand and size do...

Thanks for the help. Ok, I cleared the codes, went for a test drive, and rechecked the codes, both engine off and engine running. No codes, but the problem is still there. Start, idle, cruise, partial acceleration are all good. However, at WOT it stumbles, backfires and misses like crazy...

'93 5.0, basically stock, except for headers and PS and AC deletes. It starts fine, idles great, accelerates and cruises good; but on WOT misses and backfires like crazy. I pulled the codes and got a 96, fuel pump relay secondary circuit open. I replaced the relay, but didn't solve the...

Problem solved, finally! The stock 3 wire O2 sensors were not getting a solid ground. Replaced them with 4 wire O2 sensors with a dedicated ground. No hesitation, no backfire, more power throughout the entire range. I appreciate all the advice offered! Buddy

Jrichker, I had posted some background info in a different thread. Sorry I didn't copy it here for your info. Here is the setup, and what I've done to this point: The engine is from a '93 Mustang GT, rebuilt, installed in a Factory Five Roadster. It's stock EFI, except for the following...

Well, I'm at a dead end. I've installed and tested 4 different EGR valves with the smoke machine. (2 used, 1 new from Rockauto "Standard", 1 new Motorcraft from Rockauto) All 4 leak smoke out of the holes in the EGR housing. I don't understand why they're leaking - could all 4 be faulty? I...

187Mustang, at this point, I believe my problem is a leaking EGR valve. More specifically, the seal that the pintle shaft goes through. Since the EGR is closed when the engine is cold, and also at idle, the leak doesn't affect cold drive off or idle. However, when the engine warms up, the...

Thanks, I ordered a new Motorcraft EGR valve. Hope that will solve the problem. Buddy

How much difference in the torque curve is there between the 2 setups? (Differences in peak torque and differences in the shape of the curve itself?) Thanks. Buddy

I've been having a problem with backfire/hesitation on acceleration, after warming up. Based on feedback from previous posts, I borrowed a smoke machine to test for vacuum leaks. When I applied the smoke, it came out from the holes in the EGR valve. Is this normal? Seems like the EGR valve...

Thanks for the info, jrichker. I checked the vacuum by plugging the gauge directly into the intake where the EVR line plugs in. Had a steady 19 at 1,000 rpm. Then when I connected the EVR line using a T fitting, I couldn't keep a steady 1,000 rpm and the vacuum flucuated between 12-17...

Replaced the TFI. It's better, especially when fully heated up, but still backfires and hesitates when warm. Any other ideas or suggestions? Thanks. Buddy

Thank you for the help, Larry! I appreciate the responses. Buddy

Hello, I appreciate all the expertise offered by members. It's helped me solve a number of problems, but now I'm stumped. I've searched, but haven't found a problem exactly like this. I have a 5.0 from a 93 GT that I've installed in a Factory Five Roadster. It's stock, EFI, except for...

Where is the best place to buy a quality TFI? Thanks for the help! Buddy