Engine starts/revs but no idle
11-14-2021, 09:51 AM (This post was last modified: 11-14-2021 03:34 PM by GenkiMotors.)
Post: #1
Engine starts/revs but no idle
Hey guys! First post here. Sorry for the essay but I wanted to give as much info as possible.
I'll start by saying I have used the search on this forum and multiple others, tried everything with no results.

So I have a JDM Zenki Sprinter Trueno, the engine I bought it with was a bigport head and ae92 7 rib bottom end, got it running only to blow a rear main seal on the track due to 2 cracked piston ringlands making my oil pressure shoot sky sky. I was able to limp it back home constantly stopping to fill it with oil. I took a stock 3 rib bigport that ran fine in the car from a Zenki Levin I have as a loaner until I could get the engine rebuilt.

Took the engine apart to find it has the higher compression pistons, HKS 264 8.35 cams on both intake and exhaust, and the head has been ported/polished along with a 0.8mm head gasket. The car also has 4-2-1 headers, hollowed out cat, APEXi exhaust, Cusco MFE ECU, APEXi Super AFC, and I just installed a PLX wideband.

Luckily the crank, bores, rods, everything but the 2 cracked pistons were okay, but I put in new main and rod bearings, new oil seals for everything, and installed a new TRD 0.8mm head gasket, even new O-rings and insulators on the injectors.

After I got everything put back together exactly how I had it, the engine will crank and roughly start, but it will not idle no matter what I try. I restabbed the dizzy and took the cam cover off to confirm the dimples were aligned at 0° TDC, new cap, rotor, plugs, plug wires, even tried with a 2nd dizzy, different coil/igniter, made sure my TPS was correct, checked all the grounds I could find and still no luck. All grounds sanded down, no paint touching any of them, and yes I made sure to get the injector grounds on the intake manifold. The fuel pump is confirmed working, I replaced it when I got the car with an oem spec replacement. Fuel injectors should also be good, as I was just using them with the Levin bigport just a day before I swapped. I even tried 2 different stock ECUs just in case. I can confirm I am getting spark, fuel and compression, all cylinders tested between 225-235psi *edit:may have measured/converted wrong*. The only thing I really changed was an aluminum underdrive pulley kit on the crank and alternator, which I'll try returning to what I had before just in case.

I ran diagnostic mode and the code I'm getting when the engine is off and on is code 10, no starter signal. But the car turns over and will start/rev. I tried a different starter too but same outcome. I checked with a multimeter and found proper voltage at STA(50) on the starter, as well as proper voltage between the STA and E1 terminals on the ECU. When I try to start the car and keep it running by pressing the throttle I also get code 11, but the diagnosis manual states its fine if no code when throttle is released and activates if its pressed.

Please help me! I've been trying for a week with no luck. Thanks in advance!
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11-14-2021, 02:23 PM
Post: #2
Engine starts/revs but no idle
I would check the cam timing again. Verify that the lower crank belt gear dots align. It's easy to slightly move the lower gear while installing the belt on the upper gears.
Also, you stated you have all cylinders tested between 225-235psi. I would re-check the cylinder pressure with a different gauge. You are probably in the range of 13.5 to 14 to 1 CR ratio!!! What fuel are you going to be using. I'm assuming you do not have a knock sensor. I do not think stock pistons can live very long, if in fact you have that high of a CR. You might want to consider using a thicker head gasket or a stock head gasket.
Dave W
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11-14-2021, 03:26 PM (This post was last modified: 11-14-2021 03:33 PM by GenkiMotors.)
Post: #3
Engine starts/revs but no idle
Thanks for the response Dave, I was converting to psi from kpa as psi gauges are difficult to come by in Japan, so I may have miscalculated or cranked the engine too many times per cylinder. I'll check the timing again, but would that cause a no start signal? The timing belt was installed while the block was on an engine stand and all the timing notches line up perfectly when cylinder #1 is at TDC
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11-14-2021, 10:44 PM
Post: #4
Engine starts/revs but no idle
Probably an ecu setting issue.
Somewhere l have a translation for the MFE ecu, l'll look it up.

An analogue brain in a digital World
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11-15-2021, 12:47 AM
Post: #5
Engine starts/revs but no idle
(11-14-2021 10:44 PM)totta Crolla Wrote:  Probably an ecu setting issue.
Somewhere l have a translation for the MFE ecu, l'll look it up.

That would be awesome! Either way I'd appreciate it! I've tried using stock ECUs as well but with no luck
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11-15-2021, 04:09 AM
Post: #6
Engine starts/revs but no idle
Just checked another stock ECU and same results, but I'm not getting any error codes at all, just the 1 blink in diagnositc mode...
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11-15-2021, 09:14 AM
Post: #7
Engine starts/revs but no idle
Sounds like a real conundrum. Have you rechecked your wiring harness connections? Have seen a rough running engine that wouldn't idle before when someone had the sensor connections on the back of the head crossed, but I would expect a fancy ECU to detect such a problem.

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11-15-2021, 11:17 AM (This post was last modified: 11-15-2021 11:33 AM by GenkiMotors.)
Post: #8
Engine starts/revs but no idle
The connectors on the back are color coded, so I'm sure I didnt mix them up. I even confirmed on the other 2 stock engines near me the positioning of the connectors. *edit*just checked, green on green, brown on brown

The plot thickens...

So I bought a new timing light because I thought my old one wasnt working right. Erratic sparking on Cyl #1 sometimes nothing at all. Happened with the new timing gun too so I checked it on another car and it worked fine. Pulled my new plugs and they were black, cleaned them up and tried again. Engine ran a little better but then the erratic timing lights started to happen again. Checked my wideband and it was fairly rich. Cleaned the plugs again, and this time opened up the idle adjust screw all the way, and set my Super AFC to go as lean as possible. It still was rich but now it held a very low and unstable idle for about 15 seconds before dying.

What could be causing me to be running so rich? This was with a stock ECU, stock injectors, stock spec fuel pump. O2 sensor? My MFE ECU has a switch that disables the O2 sensor and stock fuel cut.
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11-15-2021, 11:36 AM
Post: #9
Engine starts/revs but no idle
You could try disconnecting the cold start injector to rule it out.. Have no further suggestions on what might be causing it to run rich, but it never hurts to eliminate possible causes.

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11-15-2021, 11:40 AM
Post: #10
Engine starts/revs but no idle
Thanks Ivan!
I tried disconnecting the cold start injector earlier but the same results. Its really making me pull my hair out lol
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