Odd Misfire

[STREET90]

I’m calling this misfire an odd one because I’ve have search varies forums for this type of symptom. I have cressida rebuild swap 7mgte with about 12,000 miles on it been running great until last week, it starting getting this weird misfire. It only occurs during cold start and warming up and smell of gas. The misfire will disappear when I rev it and when the engine is warmed up. I have checked the spark plugs, afm, igniter, coils, cps, fuel resistor, injectors with an ear to a screw driver to listen for the click all seem to opening normal, vacuum leaks (none) other sensors knock sensors thermostat etc, all good. Vsv's, one for the egr was not working but I don't think its causing that.:dunno:, but I replaced it with a working one. After the warming up and one minute of driving it goes away but not completely, there's a small hiccup every few seconds which I can feel through my seat and the exhaust. No codes, drives completely normal, no hiccups when boosting or cruising, although there a slight hesitation when tapping the throttle but hardly noticeable hearing inside the car maybe because my intercooling carries too much cfm for throttle to maf response. I don't think I have a head gasket issues because I never over heated, I also burp the system while the revving the engine no bubbles came, not losing any coolant. Pulls as strong as it did after the its break in

Specs:
Stock 7mgte head and bottom end
3” ddp full exhaust
2.5” intercooling with large intercooler
Custom intake
freddy bov recirculated
1.4mm mhg
stock turbo
stock injectors
Walbro 255lph
http://s995.photobucket.com/albums/af74/TheSTREET90/?action=view&current=misfire.mp4

 

[jonahs_supra]

try unplugging the cold start injector...possible its sticking open or bleeding fuel out until engine is warmed up

 

[STREET90]

I just tested the cold start injector for ohms and under startup fuel pressure it doesn't stay open or leak. Still having the misfire on startup

 

[Nick M]

How about some data to start making guesses with....Do you have fuel pressure guage to watch what it does when you are starting?

 

[STREET90]

No, I do not have a fuel pressure gauge, I'll check that the pressure regulator is working properly, I can hear fuel rushing through the fuel rail when pump is on, though its been doing that since the beginning before I had this problem. Fuel pump is working normal.

Edit: Can it be a bad injector, spray no good, or something?

 

[Nick M]

Did you jump FP to B+ in the diagnostic box? I was wondering how you heard the fuel pump over the engine.

 

[STREET90]

I don't have to, I had some issues with the fuel relay, and I couldn't locate it on the cressida chassis at the time, I grounded one of the wires from the wire looms to stay on constantly at 12v when in On mode, 13-14v when engine is running. If you listen closely for the first few seconds of the video, the electric hum/whine is the fuel pump

 

[Hotwheelsjr]

Sounds like a head gasket to me. I had the exact same symptoms on two cars before the HGs went away totally. I wasn't over heating, either, but I was loosing coolant and didn't know where it was going. Pulled the plugs and found my coolant.

 

[jg5899]

I second the head gasket, I had exact same symptoms on my car, had misfire when cold and went away when warmed up or when revved. No over heating or any other symptoms yet it turned out to be a bad head gasket.

 

[Nick M]

Constant hot pump KOEO? I hope you don't crash your car.

 

[STREET90]

Yea, was going make a separate switch for it but went this method, and thats what battery switches are for.

I still don't think its a head gasket, because I've experienced two bhg's on two NA motors and the symptoms not are the same in motor vacuum, When I checked the spark plugs I also looked inside the cylinders with a led light, all I saw was carbon build up. I'm not losing any coolant, I burped the system by letting the engine run for 25 mins at normal op temps, even revving to almost redline, no overheating issues, most of the time the temps is below the half point when driven and idling. no coolant in the cylinders, coolant level in overflow tank never changes. Tested the injectors' resistance today all are in spec, but the spray may be faulty or clogged, But I will do a compression test.

 

[STREET90]

Okay so I did a compression test, everything is still within the tsrm spec, Cylinder one may have a bad valve or rings? pulled the spark plug wire and injector misfire is still there
1. 135
2. 170
3. 160
4. 150
5. 170
6. 160

 

[Nick M]

Or the cross hatch is worn. That does happen, even on a Toyota.

 

[STREET90]

So I may have so internal issues valves, rings, cylinder wall gazed or damage, I'm not saying head gasket though:nono:. But started pulling out spark wires while the engine was running, Cylinder one had no effect when pulled. When the engine is revved plugged and unplugged made a difference, engine ran smoother, I replaced the #one spark plug and it made very little difference misfire is still and smell of gas is still there. So I will check the injector next maybe its clogged or staying open too much even though it still clicks.

 

[STREET90]

So update, the misfire got so bad that I could've the car anymore because it almost stalls at lights and idles at 400rpm. So I stop driving it and began work, replaced the injectors with cleaned and flowed ones and a new fuel filter as the old one was very dirty, I've checked and cleaned the ICV, egr and the airways, and TPS, fuel rail, and cold start injector even ultrasonic the fuel pressure regulator which by the way has a huge dent on the side that could be preventing the valve from increasing pressure, and checked the timing belt and cams. I still have the misfire but drivability has gotten better but power lost was not recovered and I still smell gas, even after replacing all copper washers and o rings. The only things I haven't checked is the ECU itself and timing with a timing light. My assumption is that maybe my AFM or ECU is bad in someplace because when I initially started the car code 24 would pop up but goes away the afm was plugged in when I start it but the I forgot to plug in one of the knock sensors. Still no overheating even with AC on, no bubbles from coming through radiator, coolant is still green, no smoke not even a puff from where I can see. misfire clears up when revved. I'll so an oil changed to see any pieces of rings something made it to the filter or pan. Still puzzled:dunno:

 

[adampecush]

puzzled? your ringlands are likely blown on #1 with that compression. IIRC, tsrm specifies max difference of 15 psi between cylinders as well. If you disconnect your egr to the manifold, you will probably push oil through your air filter. If you richen up the mix at idle, your miss will probably go away. You also won't see any sign of the ringlands as the rings are still holding them in place. Good luck

 

[ma70t]

Bhg check ur plug I bet one is getting wet with coolant

 

[Backlash2032]

.....everyone needs to stop throwing out blown head gasket at the slightest of things.

Might be blown head gasket because it has low compression on one cylinder and a miss.

On the other hand... Might be damaged rings/ringlands/cylinder because theres low compression and a miss. BUT it doesn't burn coolant, the pistons are dry, the overflow doesn't overflow, the engine doesn't overheat, and the head gasket usually goes on no. 6 first.

Which makes more sense?

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[STREET90]

Thaaannkk you ^ it was rings and cylinder wall