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G4+ plugin for gen 1 3sgte MAP sensor question


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Good day everyone,

I have a G4+ plugin ECU for a 1991 Toyota MR2. The car has been running well for over a year with no issues. One Monday I start the car like any other time and it runs as expected for the small local trip. I get home and park until the next day. The following day i start up the car no problem. warms up like normal. i pull out of driveway and all of a sudden car bogs and stalls. i barely make it around the block and park in driveway. now when i start it barely runs before stalling. I hook up the laptop and connect to Ecu. The only way I can get car to idle somewhat normally (15.6 AFR) is by unplugging IAT sensor which gives a IAT of -40 degrees Celsius. from my understanding, doing this adds fuel? somethings i noticed and have questions about are the general runtime values MAP (psi) and MGP (psi). When i unplug the IAT and engine idle smooths out, I noticed MAP at 6.8 psi and MGP at -7.4 psi. my external Boost gauge reads -21" wc (which is normal) when i reconnect IAT, MAP reads 11.6 psi idle becomes rough and my external boost gauge drops to - 8-10" wc. Can someone clarify which parameter, if any,  MAP or MGP is suppose to match my boost gauge? all these readings are at idle. Im beginning to question the MAP sensor. I am using the MAP sensor provided by CRW when I bought the ECU last year. There are no part numbers on the sensor. sensor type selected was Cal 5. Can someone point me in the right direction?

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MGP should roughly match your gauge. (MGP = Manifold Gauge Pressure). -21" is -10.3 psi so while its not dead on, its in the same ballpark. Also, -7.4psi MGP sounds like a reasonable number for idle vacuum. When the engine is off, but ECU on, does it read roughly 14.7psi/101kpa? If this checks out, i'd say your MAP sensor is reasonably healthy.

Do any other sensor values jump out at you as wrong? hit f12 and have a look at the various runtime value and if anything looks completely out of line with reality (eg when its cold with ECU on and engine off, most temps will be within 5deg of ambient).

When its running badly with everything plugged in, is your AFR high or low? can you post a log and your pclr please?



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Attached is a copy of the current base map and a 10 min idle log after cold start. The only way I can get the car to run somewhat normal is by unplugging my IAT sensor. in the log i connect the sensor a few times and car dies. The car was remotely tuned over a year ago and has never had an issue. From my understanding it is running off my AEM Uego ? I was wondering if maybe my Bosch LSU 4.9 O2 sensor may be in need of replacement. Thank you all in advance.

issue with iat.pclr

log issue with iat.llg

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Ok, you are very lean for some reason.  When you unplug the IAT sensor it defaults to your error value of -40°C which adds 26% more fuel.  

Since nothing has changed ECU/Map wise you need to look at why the engine is suddenly getting ~30% less fuel.  Start by checking fuel pressure - it could be the fuel pump or FPR dying or a blocked filter etc. If pressure looks ok then I would have the injectors inspected. 

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