Author Topic: Fuel cut, hesitation, breaking up???  (Read 3375 times)

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Offline awfc3s

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Fuel cut, hesitation, breaking up???
« on: April 27, 2018, 05:26:29 AM »
I drove the car for the first time to work yesterday with no problems. Felt great. Drove it home, felt great. Went to fill up before going to the movies, felt great. Drove to the movies, felt great/didn't notice anything. Got out of the movies and the car was breaking up under medium load. If I got into boost it would break up through out the rpm range. I put too much premix in when I got gas because my fuel gauge apparently reads 1/4 lower than what it really is. On the way home I stopped and put in another 2.5 gallons of 93 to try to even it out. Not sure if I got bad gas or if something else is going on. Going to pull the plugs this evening. I'm also considering draining the tank. Only difference was that I drove home at night, so my headlights were on. Not sure if I have a grounding issue. Just to note, I can get through the rpm range, but it's painful. Just about everything under the hood is new or newer, this is not going to be fun.

I should also mention that turbos are parallel and running a Haltech platinum sprint RE ECU.
'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline murz

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Re: Fuel cut, hesitation, breaking up???
« Reply #1 on: April 27, 2018, 06:30:06 AM »
Can you get through the rpms entirely at low load? I wonder if something came disconnected.
1986 AS GXL Turbo swapped
1993 VR R1

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #2 on: April 27, 2018, 06:38:55 AM »
If I am cruising on light load it's almost as if there isn't a problem. Car seems to idle fine. I haven't tried free revving. I don't think it's fuel cut cause that's a pretty violent feeling. It's more like an ignition cut.
'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #3 on: April 27, 2018, 06:57:24 AM »
Now that I think about it, I had a similar issue/feeling on my motorcycle. Changed the plugs and it all went away. So I am hoping that that is the issue.
'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline murz

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Re: Fuel cut, hesitation, breaking up???
« Reply #4 on: April 27, 2018, 08:20:21 AM »
Speaking of plugs, I need to change mine out sooner than later as well. I wonder if it could be a bad coil?
1986 AS GXL Turbo swapped
1993 VR R1

Offline ITSWILL

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Re: Fuel cut, hesitation, breaking up???
« Reply #5 on: April 27, 2018, 01:34:53 PM »
If it's only under load I guess is could be pre igniting. However I would t expect it unless you were really boosting.
86 Base LS1 w/100 shot
88 TII 20B T70 turbo

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #6 on: April 30, 2018, 09:47:54 AM »
So this is an account of everything from this past weekend:

Thursday morning 4/26: Drove car to work in the (30 miles). No problems got into boost maybe 2 times.

Thursday afternoon 4/26: Drove home from work (30 miles). No problems. Boosted very little. Stopped to get gas before getting to house. Put 14 oz of Idemitsu premix in the tank, but only 9 gallons of fuel went in (gauge reads 1/4 lower than what it should, maybe bent float on pump).

Thursday evening 4/26: Drove to movies (20 miles). Very little time spent in boost. No problems. Parked car for 3 hours.

Thursday night 4/26: Leaving movies. Started car. Exhaust smoked a little more than normal on cold start, didn't think much of it. Drove fine until under load and in boost. Started breaking up/misfiring throughout rpm range under boost. Thought I might have gotten bad fuel or I over premixed. stopped at gas station to add an additional 2.5 gallons to help even out the amount of premix. Still getting breaking up. Got home and parked car. Idle sounded "off" slightly. Shut car down and went in for the night.

Friday evening 4/27: Pulled spark plugs. They were "dirty", but didn't look fouled. Changed plugs anyways, 9's on all 4. Checked spark by holding plug near ground on all wires. Had spark. Went for test drive. Still breaking up. AFR's were reading 10s-11s under boost. Engine temp was fine. Oil pressure was about 100 under full throttle. next I decided to drain the fuel tank. I thought, maybe it was bad fuel or I accidentally put in 87 just out of habit from the daily. Drained tank and put 2 gallons of new 93 fuel in with 0.75 oz/gal of premix. Took it for a drive. Still breaking up. Now I am building so much crankcase pressure that I blew the dipstick up and oil shot everywhere under the hood. Next I checked compression on both rotors only on the leading plugs. Compression gauge is cheap and doesn't read full pressure (tested against 160 psi of air pressure and it read 120 psi). Got even bumps on each face on both rotors at 60 psi (remember gauge reads low so should be 100 psi). If they indeed were at 60 psi, I doubt the car would even start or be able to stay running under its own power.

Saturday morning 4/28: Tested resistance of leading coil. FSM states plug pins should read below 1 ohm. I got 1.5 ohms. High tension leads should read between 9.6 and 16 ohms I got 12.25 ohms. I thought the coil was the problem, but then I tested the 2 trailing coils and got the same readings on the electrical connection of 1.5 ohms. I don't think that all 3 of my coils could be bad and have failed at the same time.

Sunday 4/29: Took oil cap off and disconnected out line from catch can going to turbo inlet. Zip tied a paper towel around both locations to help relieve pressure build up. Test drove. Still breaking up, but dip stick stayed in. Towels not covered in oil. Hooked laptop up to Haltech to try and see if there was any data that would scream at me. I really don't know much of what I was looking at, so not sure it did me any good. Went for a test run and did some data logging. Car is running super rough at this point (sounds like it's firing on one rotor). Sounds like it has a cam. Getting harder to start without giving it a little throttle. Will also die after running on its own power for several minutes. Decided to change the fuel filter. Test run, nothing changed except I blew oil all over my engine bay again (soaked throw the paper towel). I took the intake side off of the throttle body and saw no oil in the intercooler piping or intake. I did see oil behind the butterfly valves on the throttle body (engine side). No oil on the turbo side either. Turbo forward (still twin ran in parallel) had no play or oil on turbine. No oil on intercooler piping for hot side. Did another compression test and got same results as before. Last thing I checked was the brass filter on the catch can. Didn't see anything really clogging the filter or that screamed at me there was an issue. There are a few things that I didn't get a chance to test yet. The resistance of the plug wires and the igniter. Again, I think I have 2 separate issues now, but I am at a complete loss.

Including a picture of a data log run. The lean peaks are from letting off (lean out on decel is still activated)
« Last Edit: April 30, 2018, 09:55:00 AM by awfc3s »
'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #7 on: April 30, 2018, 10:48:15 AM »
You are not allowed to view links. Register or Login - driving (hard to hear the breaking up, but it's there trust me)

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'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline murz

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Re: Fuel cut, hesitation, breaking up???
« Reply #8 on: April 30, 2018, 03:14:32 PM »
Any backfiring/ more backfiring than normal? Crank sensor come loose or something?
1986 AS GXL Turbo swapped
1993 VR R1

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #9 on: April 30, 2018, 06:26:05 PM »
No backfiring. All sensors seem to be plugged in and where they need to be.
'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline toplessFC3Sman

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Re: Fuel cut, hesitation, breaking up???
« Reply #10 on: May 01, 2018, 06:55:34 AM »
Just because you're getting spark outside of the engine doesn't mean that the coils aren't going bad - the higher the boost, the harder it is for spark to bridge the gap, which means it finds other paths out. This could be a crack or break in the plug wire insulation, along some grease on the plug to the engine block, through some insulation internal to the coil, etc. I'd take the ignition system apart and clean out all the connectors/plugs, check for insulation cracking, and put just a dab of dielectric grease on the conductor within the spark wire.

Also, do you still have an EGR system or catalysts? If so, try blocking the EGR valve off to rule out a leaking valve, and if you have a cat, make sure its not crumbling or blocking the exhaust

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #11 on: May 01, 2018, 07:23:02 AM »
I haven't inspected the wires for any cracks. They were brand new, but I guess anything could happen. There are new plugs in there and I did put dielectric grease on the leads. No egr or cats. Like I said in a previous post. My coil packs are all reading at 1.5 ohms (completely disconnected from everything). So I can't imagine that all 3 are bad at the exact same time.
'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline murz

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Re: Fuel cut, hesitation, breaking up???
« Reply #12 on: May 01, 2018, 09:45:01 AM »
Bad ground at all? When I bought my car I re-did a few of the grounds with some heavier duty cable, which has fixed the hesitation I had when I bought it.
1986 AS GXL Turbo swapped
1993 VR R1

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #13 on: May 01, 2018, 10:24:55 AM »
I guess it could be a ground, but it has a brand new harness on it and was fine for 1,100 miles. Why fail now?
'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring

Offline awfc3s

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Re: Fuel cut, hesitation, breaking up???
« Reply #14 on: May 18, 2018, 10:18:55 AM »
Just wanted to post an update on this. Decided to do another compression test when I got back from my trip. Got a nice new OTC gauge. And.... The front rotor is down an apex seal. getting only 1 bump at like 40-50 psi. Super upset since this engine only has 1,100 miles. Still not sure if it was tuning or assembly, but if I can determine that it was assembly, you can guarantee I will be telling everyone about the company that built this engine for my friend prior to me owning it. Going to pull the engine this weekend. :'( It is bitter sweet, because I know what the problem is now, but the fact that I have to rebuild an engine that was just rebuilt sucks. I am looking forward to the rebuild though as this will be my first rotary rebuild and I'm excited about the opportunity and what I will learn. Got myself a good FSM and plenty of work space, so hopefully it goes smoothly. Hoping to get this thing back on the road relatively quick. You can best believe that I will be taking it to the tuner asap once the engine is back in the car.

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'88 SE LSX (Dead)
'87 LSX drift car
'90 TurboII vert
'94 Silver Stone Metallic Touring