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HybridZ

Running Rich, sputtering


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I have come a long way with this car but can't figure this one out. Cranks right up, sputters, black smoke, the smell of gas is strong. It runs OK but rough if I drive it.

Recently cleaned a lot of crud out of the tank.

Replaced plugs with NGK

New wires, cap rotor

New CHTS

Cleaned all sensor connectors.

Replaced all vacuum lines

 

Fuel pressure is running at 30. When I disconnect the regulator vacuum line it pops up to 34 so it appears the regulator is working properly. There is no gas in the vacuum line. When I stop the engine the pressure gauge pops immediately to 25 but doesn't move, even after several minutes. Thinking the injectors are NOT leaking.

 

Also the vacuum is running low. It's between 5 at rough idle and 13 at higher rpm.

I'm wondering if the injectors are dirty and staying open too long. We had the car running well BEFORE I drove it the first time. I'm guessing the drive shook up some of the crud in the tank (there was a LOT!) and caused the filter to clog. I'm also guessing some of the finer crud got through and has clogged the injectors.

Put a can of Seafoam in the tank and let it idle for 40 minutes. I don't think it helped at all.

 

Not sure what to try next...

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Anything fine enough to get through the filter wouldn't clog the injectors methinks. Unless the line itself had crud in it already past the filter. And if the injectors were clogged they probably wouldn't run rich unless they were just leaking. If you can't find anything wrong with the fuel then perhaps investigate the numerator. Induction leak? Anything that might throw off a maf reading if you have one.

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Also is there a serious loss of power? Perhaps it smells like unspent fuel not because it's running very rich but rather incomplete burn. The wrong type of plugs, or in your case fouled plugs, or clogged injectors will do that easily, but you'd probably notice a power loss besides just running rough. Clean the plugs and test the injectors in a cup if you can.

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The power is pretty good. The plugs are brand new. I don't have a way to test the injectors. I went through the fuel rail 6 months ago and replaced several frozen injectors by swapping them from an 83 parts car. Then I had another injector lock up, replaced it Monday. It is a PITA to get the fuel rail off this car.

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There is no MAF. This year has an AFM. I checked the settings yesterday and they are factory. The silicone glue has not been touched. If the air induction is leaking between the AFM and the injectors, wouldn't it be running lean? It's not backfiring at all which is good. When I had low fuel pressure from the clogged lines it was backfiring a lot.

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Um, the fuel pressure should be a lot higher than that, I think the with regulator unplugged it should be about 38-40psi. Sounds like your fuel pump might be failing. Also, the engine should pull about 20in of vacuum at idle. You must have a vacuum leak somewhere. A plugged exhaust will also cause low vacuum readings. Hope this helps!

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Um, the fuel pressure should be a lot higher than that, I think the with regulator unplugged it should be about 38-40psi. Sounds like your fuel pump might be failing. Also, the engine should pull about 20in of vacuum at idle. You must have a vacuum leak somewhere. A plugged exhaust will also cause low vacuum readings. Hope this helps!

 

I just replaced the fuel pump with a new one. I plugged the throttle body and blew through a vacuum line to see if it held pressure and found a few small leaks. I will try it again. But I have replaced every line except for the one under the intake.

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you said it's running rough , misfired rough ? ignition misfired will have raw gas smell . your vac is too low at idle will cause fuel press. to be higher .

Yes it is misfiring. I'm getting a good spark at every plug. I guess I should check the timing even though it hasn't been touched since it was running OK

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You said it isn't backfiring at all? Backfiring goes hand in hand with an excessively rich mixture though doesn't it? Which also goes with the smell of unspent fuel. That is quite the paradox...

 

Brand new or not, the plugs could have fouled right after the first run from bad gas etc. I think the key here is that it was running fine at the start. If the pump was crap or something like that, you wouldn't have had any good luck at all. You just have to figure out what was totally fine until a touch and go could have spoiled it.

 

Bad timing will also result in a serious loss of power, which I'm still not sure you have ?

 

Seems like vacuum leak and low fuel pressure are at the top of the list. In my experience injectors are pretty sensitive--if they are not spoon fed they can make the engine miserable. Whether they are really clogged or not, an irregular spray can even cause a rough run, I've had injectors come straight from overhaul that didn't spray consistently enough to make it purr.

 

Also I don't think anyone has mentioned o2 sensors if you got em. Does it run worse cold or after it's thoroughly warmed up?

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You said it isn't backfiring at all? Backfiring goes hand in hand with an excessively rich mixture though doesn't it? Which also goes with the smell of unspent fuel. That is quite the paradox...

 

Brand new or not, the plugs could have fouled right after the first run from bad gas etc. I think the key here is that it was running fine at the start. If the pump was crap or something like that, you wouldn't have had any good luck at all. You just have to figure out what was totally fine until a touch and go could have spoiled it.

 

Bad timing will also result in a serious loss of power, which I'm still not sure you have ?

 

Seems like vacuum leak and low fuel pressure are at the top of the list. In my experience injectors are pretty sensitive--if they are not spoon fed they can make the engine miserable. Whether they are really clogged or not, an irregular spray can even cause a rough run, I've had injectors come straight from overhaul that didn't spray consistently enough to make it purr.

 

Also I don't think anyone has mentioned o2 sensors if you got em. Does it run worse cold or after it's thoroughly warmed up?

THe 79 didn't have 02 sensors. It doesn't seem to run any different when warm. I'm on my 3rd set of plugs. I really don't think that's the problem. The last set I installed just the other day and it ran just as bad. I'm about to go through the vacuum system again. Will also check the timing. I will upload a video later as well.

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Wow I totally know that too.... space case here. AFM.

 

Thermo-time switch? This would keep the cold start injector OPEN causing it to run rich.

According to the manual the cold start injector ONLY gets pulsed while the starter is running. The thermo-time switch bypasses it if the engine is warm. Either way I have checked the cold start injector for leaks and tried disconnecting it with no change to the engine.

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According to the manual the cold start injector ONLY gets pulsed while the starter is running. The thermo-time switch bypasses it if the engine is warm. Either way I have checked the cold start injector for leaks and tried disconnecting it with no change to the engine.

 

You seem to have your ducks in a row. Have you checked the water temp sensor too?

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You seem to have your ducks in a row. Have you checked the water temp sensor too?

Yes, replaced it already but I think the old one was OK.

The problem is a short in the connector at the ECU. I just tweaked the sockets in the connector so they would make better contact. Some where bent back pretty bad. It cranked and ran OK so I drove it. It ran great for a few minutes then started sputtering a little. It seems if I hold back on the cable it runs great. Still troubleshooting

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Spoke with a good Zcar mechanic and he diagnosed with me over the phone. Looks like the harness from the coolant temp sensor/thermotime sensor is bad. Ordered a new one from Courtesy Parts out of Dallas. Hope to get it installed Monday.

There was a problem with the ECU and I have fixed that but it was still not quite right.

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  • 4 weeks later...

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