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Challange: Lotus Esprit GM fuel injection mystery misfire?

Discussion in 'Technical Q&A' started by thecarreaper, Mar 1, 2015.

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  1. thecarreaper

    thecarreaper F1 World Champ
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    #1 thecarreaper, Mar 1, 2015
    Try to keep this short:
    Bought a 1990 Lotus Esprit from a dealer off of a Lotus message board.
    Car had a rebuilt engine with 600 miles on it, and lots of well done upgrades.
    Soon as car was delivered it developed a lean misfire on cylinder 2 and 3.
    This is the really odd part:
    My friends and I have had many cars, and 3 lotus esprit's before. We are not new to this.
    We have replaced: the computer with a new one, the computer chip, all of the injectors, all of the engine sensors, new battery, fresh fuel, every part of the ignition system.
    I even built, an Windows XP 32 bit laptop, with a freaking serial port to talk to the the ecu and do Excel data recordings in real time. I have NO check engine light, but a terrible lean misfire on 2/3 and the car has not been drivable for months. Will not take any throttle, ie it shuts off when you open the throttle in gear.

    Numbers: Compression ( this is a fresh built engine and turbo) 160 psi on all 4.
    fuel pressure: 44-50 psi, 30-35 psi after 2 hours sitting.
    New five-0 motorsports main and secondary injectors.
    All new sensors, I mean every damn one of them.
    Vacuum: erratic 7-9 in/hg on both of the main port that control MAP sensor and fuel pressure regulator.
    Intake and plenum has been smoke checked: NO LEAKS.
    Head gasket is good: no oil / water leaks or mixing.
    Oil pressure is good, have replaced oil and filter due to the lack of use.
    AC blows ice cold, which means the idle enrichment circuit in the ecu works when the AC is selected on. ( Car has a Air / fuel ratio gauge)

    Replaced battery and have ensured all the sensors and ecu are sending / receiving book voltages or grounds.

    * Right now all of the vacuum lines and ports have been plugged, with the exception of the map and fuel pressure regulator ports. All the vacuum lines are new and to the factory routing spec.
    Car runs BETTER if you pull of a plug wire or injector plug from 2/3 while running, its running on 1/4 only.

    I pulled the whole injection harness out and rang it with a meter, then put NOID lights in the injection connectors and ran 12v and ground signals with a Powerprobe 3 tool. No faults found. Rang out ECU harness from the plug at the computer to each and every sensor, and injector. This took me 3 weeks, and I found nothing wrong.


    Note: Injectors 1/4 and 2/3 use the same matched drivers for injection and ignition firing. This is all controlled by the ECU and the old ecu and the new one have the exact same misfire. Have swapped and replaced the ignition coils, wires, ignition module and gone through 4 sets or NGK iridium and standard Lotus spark plugs.


    I had $20k in the car and the dealer in Florida has offered to buy it back for $8000.00. They will be here in two weeks to get the car.


    I would love to see if anyone thinks I missed something simple, as these cars use a simple GM fuel injection system. The car has beaten me, plus 4 other tech- mechanics.



    Thank you for taking the time to read this. :)
     
  2. thecarreaper

    thecarreaper F1 World Champ
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    #2 thecarreaper, Mar 1, 2015
    Last edited by a moderator: Sep 7, 2017
  3. badkarma308

    badkarma308 Karting

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    #3 badkarma308, Mar 1, 2015
    Have you checked fuel pressure under load? I had similar shenanigans on my turbocharged Ranger, turned out I had an almost completely clogged fuel pickup sock. It was just enough to get the fuel I needed at idle and low load, but as soon as load and boost increased, fuel pressure dropped right off. Also found a torn diaphragm in my adjustable fuel pressure regulator in the process, but the sock was the problem.
     
  4. thecarreaper

    thecarreaper F1 World Champ
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    #4 thecarreaper, Mar 1, 2015
    Last edited by a moderator: Sep 7, 2017
    I may pull the pump out and have a look. I bought a pump, but have not put it in. I did change the filter, and the nominal pressure in the manual states 33-55 PSI, so my 40-50 psi should be OK.

    Found an issue today: 11.36 volts at the injection harness orange/white wire. Should be battery voltage (?) which reads 13.86 running.

    The other two wires are the driver circuit wires for 2/3 and 1/4 cylinders. They go by ohms through the boards on the ecu. I have the factory Lotus service manuals. Trying to figure out what to look at next.
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  5. kingsdare

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    #5 kingsdare, Mar 1, 2015
    The above tells me you have a cracked or leaking head gasket between cylinders 2 and 3.

    Check it with a leakdown tester to verify.
     
  6. smg2

    smg2 F1 World Champ
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    #6 smg2, Mar 1, 2015
    The erratic vacuum at idle stands out. Have you done a leak down?

    Looking at the schematic the injectors should be low impedance ~2ohm I'm assuming that's the kind you have?

    I have experienced something similar on a Esprit, turned out that one of the injectors was saturating and the coil was failing after a bit of running. Needed a scope to see the impulse waveform though. Bad ballast and old injector. That may not be your issue but you never know. Though the erratic vacuum points to sticky valves or possible lifter issues.
     
  7. Cribbj

    Cribbj Formula 3
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    #7 Cribbj, Mar 1, 2015
    Have you confirmed the ignition is actually firing the plugs?

    From the schematic there are jumpers for P&H injectors on the ECU. Presumably you can run either high impedance, saturated type, or low impedance P&H type. If you're running low impedance P&H, are those jumpers in place?

    Have you tried moving injectors and coils around to see if you can get the problem to move?
     
  8. JG333SP

    JG333SP Formula 3

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    #8 JG333SP, Mar 1, 2015
    This sounds MADDENING. I think I'm cured from wanting one of these. I'm def interested in hearing if it's a leaking head gasket on a 600 mi engine. Did the dealer happen to do the engine rebuild work?
     
  9. thecarreaper

    thecarreaper F1 World Champ
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    #9 thecarreaper, Mar 1, 2015
    Thank you all for the excellent replies. I have not done a leak down, but we have verified with a tester and replaced everything in the ignition. Head gasket seems unlikely but it is an excellent point given the erratic vacuum signals on the ports. If its bad, its not loosing oil or water, yet.

    I found the orange and white wire has 11.36 volts on it, it is supposed to have battery voltage on it, which was reading 13.86 at other locations.

    Back traced that wire to the fuel pump relay and "rollover" switch circuit and I have the same low voltage. Seems the fuel pump may be bad, dragging the injector circuit down?

    Going to work on it more this week, we may as well do a leak down too, since I am going to have it towed, (again) to my friends shop.
    I really hope the ecu injector driver circuit has not been damaged. I just put in a new ecu, chip and memcal!

    I sold my 328GTS to Germany in December, and think I want a 2002 Ram Air 6 speed Trans Am. :) Have not had one of those yet.

    Has to be better car than these Lotus cars are. :)

    Thanks for the ideas and support. Will update asap.
     
  10. wax

    wax Five Time F1 World Champ
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    #10 wax, Mar 1, 2015
    That's saying a lot, as you've had hundreds in just about every other configuration. ;)



    Sent from my iPhone using Tapatalk
     
  11. finnerty

    finnerty F1 World Champ

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    #11 finnerty, Mar 2, 2015
    Last edited: Mar 2, 2015
    Sounds like you have 2 problems....yes ?

    1) A vacuum (leak)
    2) A lean misfire related to fuel delivery

    Either they are independent or related.

    If related, the only thing I can think of that may be a common fault would be the fuel pressure regulator --- more specifically, a vacuum leak in that device or its supply line / connections.
    This would account for your erratic vacuum, and possibly could account for the lean mixture on 2/3 if the fuel pressure is fluctuating in the injector delivery rail. Inconsistent pressure could only affect 1, 2, or 3 of the injectors..... it does not necessarily have to affect all 4.

    I would put a fuel pressure gauge on the test port in the rail and look for small fluctuations with the engine running.

    The Service Notes give test instructions for verifying / diagnosing the pressure regulator.

    ... just a thought.

    Also, as just for the lean problem independently, have you checked for open / ground faults in the injector 2/3 peak and hold circuit ? That could easily cause the injectors to run lean.

    +++++++++++++

    Another thought ---- how are the O2 sensor(s) ? I might check them out as well.


    .
     
  12. thecarreaper

    thecarreaper F1 World Champ
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    #12 thecarreaper, Mar 3, 2015
    Thank you.
    I have asked about the fuel pressure regulator, and keep getting told they don't go bad. (I don't believe that.) I got the car to run on all 4 last night, for 4 minutes.
    I have found bad pin connections, and two wires that have gotten hot, and I suspect are bad. These wires feed 12v to the fuel pump, fuel pump relay and the 12v feed for the injection harness. I am also going to replace the fuel pump, strainer and pulsation dampener.

    I have had the car listed for a few months on the Lotus board for $12500 as is with full disclosure and now have several people interested in the car as is, as it sits. I intend to fix it and sell it or sell it as it sits.

    But I will update the thread.

    Right now my plan is to keep working on it this week, unless someone makes an effort to come here and buy it. Fixed, I think i can get $18-20k for it.


    I just want something to drive besides my f150. I want to go back to school and get my Masters, since I earned my BS degree from ERAU last October.
     
  13. andecorp

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    #13 andecorp, Mar 3, 2015
    Esprits are more reliable than any Lambo or Ferrari of the same vintage. As long as they are looked after properly and not played with by people that shouldn't touch them (whoever re-built it).
     
  14. smg2

    smg2 F1 World Champ
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    #14 smg2, Mar 3, 2015
    Low fuel pressure would not result in a specific cylinder misfire, it'd travel about. The fluctuating vacuum gauge points to mechanical issues, either sticking valves or a leak. From what I recall the tappets are hydrolic and that can make problems when they collapse.
     
  15. andecorp

    andecorp Formula 3

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    #15 andecorp, Mar 3, 2015
    My in-house mechanic is ex-service head of Lotus Australia for 20 years and he also helped build the '90s Esprit LeMans racers. He's "God" when it comes to Esprits.

    He said to check the intake manifold. It sounds like it's clogged up with gung from bad fuel close to the MAP sensor.
     
  16. Mark 328

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    #16 Mark 328, Mar 4, 2015
    I would recommend you start to look at the valve train, start with the gaps then measure how much they open, and finally perform a leak-down test.
    I had a cracked valve seat and it was an intermittent problem. I took the car to the dealer and they said it had lower pressure but did not think the low pressure was the root-cause. In my Dodge the problem would come and go.
     
  17. thecarreaper

    thecarreaper F1 World Champ
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    #17 thecarreaper, Mar 4, 2015
    Thank you. The pulsation from both the forward and aft factory vacuum ports does have me concerned still.
    Jumpered the fuel pump circuit after finding the fuel pump ground was spiced to an electric charge-cooler pump, and the car runs well. ( but not perfect)

    Still have the hot / damaged wires and at least 3 pins to replace.
     
  18. classic308

    classic308 F1 Veteran

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    #18 classic308, Mar 6, 2015
    Any updates?
     
  19. thecarreaper

    thecarreaper F1 World Champ
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    #19 thecarreaper, Mar 8, 2015
    Sorry. Been distracted. Replaced the fuel pump as it tested bad, rewired the relay and fuse circuit for the fuel pump, added a dedicated ground for the fuel pump, as they had a chargecooler pump and oil cooler fans running from a common ground. Car runs , got to finish cleaning up the wiring and rear compartment.
     
  20. thecarreaper

    thecarreaper F1 World Champ
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    #20 thecarreaper, Mar 9, 2015
    Last edited by a moderator: Sep 7, 2017
    Rewired the fuel pump relay back to a stock configuration (according to factory wire diagram). Replaced the bad pin on the orange wire with white stripe, replaced 2 bad connectors, grounded the fuel pump relay and the fuel pump by themselves- the chargecooler pump and the cooling fan for the added oil cooler were all sharing the same ground- now they have separate, dedicated grounds. We have full voltage to the injection harness and the car runs on all 4 cylinders. I also replaced the damn fuel pump and strainer this weekend as well. Lotus Map Sensor from SJ Sportscars came in, installed it as well. (Made no difference, but what the heck.)


    I have several interested people in the car. I am going to give a few people a shot at seeing the car this weekend as is, for the $12500 in my Lotus cars for sale ad. After that its going on Ebay internationally with a low reserve. I want a ram air trans am for some reason.
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