AMC 401 bizarre problems (EBL system)

FrankNB

Hi, I'm throwing this out here cause I'm a bit mystified with a problem I've been experiencing with the 401. Back in late October I replaced spark plugs (regular copper plugs) gapped to 0.060", cap and rotor (msd billet distrib), MSD TFI coil. I was having a lot of backfiring during decompression stopping (manual tranny) before the plug change and the plugs fixed that initially. Then, my fuel mappings seemed all off (Dynamic EFI EBL with 454 Holley TBI, 80lb at 26psi), that I had to enrich and recenter the table by almost 10%. Eventually I got it all tuned up again . A month later, I drive 80km on the highway all was working well. I park it overnight then suddenly the next morning the damn thing runs way lean again. This time I had to re-center the fuel map table by another 20% and it's been running like crap ever since. So two days ago I checked all the vacuum lines, replaced the broken ones and same with vacuum port plugs. I then added some fuel injector cleaner in the gas tank, some Seafoam (yea I'm that desperate) through the brake booster vac hose and half a can in the gas tank too. Not much change yet. I've checked the fuel pressure and it's at a steady 28 psi and tomorrow I'm going to pick up a cylinder compression tester to make sure there's nothing catastrophic there. The temperatures have been dropping steadily outside, but I mean I've ran the jeep for two years with the same fuel mapping until last October. I just don't know anymore, I might put back the old TFI coil and see how things go from there. Any suggestions; cleaning the IAC, the injectors, map sensor or something? Thanks for any input.

tufcj

I don't know anything about Dynamic EFI, but I'd start there. If nothing else changed, and suddenly you're running lean, then the EFI is or isn't doing something. Does it run in closed loop (O2 sensor)? Can you plug in a PC and look at settings like IAC position, TPS position throughout the RPM range? Does Dynamic have a tech hotline or troubleshooting manual? Bob tufcj

FrankNB

Yea, I have both a NB and WB O2 so I can run the system in open loop using the WB to learn. Once that is set, I can run closed loop with the NB. It's all live with a laptop while the jeep is running, and can flash on the fly. It's a pretty neat system. I'll do some research in cleaning the injectors and maybe start replacing IAC and Map sensors. But I'll start with compression testing and using the other coil. Here starts a game of process of elimination in -15C, sucks! I should add I posted in the forum where most of the support for the product goes on, but nothing really useful was suggested. There's gotta be something mechanical going on. I was thinking since the jeep is not driven regularly that some form of wax or varnish might be accumulating somewhere.. trying to come up with any possible gremlin I can think up..

tufcj

Have you checked fuel pressure at running RPM? Could be your fuel pump can't move enough volume at speed. Could also be a partially clogged fuel filter. Low fuel pressure could cause a lean condition. Bob tufcj

FrankNB

Well, after months of banging my head against the wall.. I resealed the intake, changed fuel pump and all the sensors in the fuel and exhaust systems. Last piece of the puzzle, those mofo injectors. Got new injectors from Holley and all is back to normal and had to revert to the original fuel maps and all. Figured I'd put this update in case someone gives a darn.

Dusty

FrankNB;133801 wrote
Well, after months of banging my head against the wall.. I resealed the intake, changed fuel pump and all the sensors in the fuel and exhaust systems. Last piece of the puzzle, those mofo injectors. Got new injectors from Holley and all is back to normal and had to revert to the original fuel maps and all. Figured I'd put this update in case someone gives a darn.

id be checking IAC. they hang up. next fuel map it it a one wire or heated O2? bmps help a lot. i wouldn’t chang anything else including fuel map until you figure out why it changed suddenly id go back to the 10% map if that ran.

BTW do you have spark control? speed sensor? whats the map reading did map fail;?