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Discussion Starter · #1 ·
Hello all.

I have a 2002 Spyder that was 2ZZ swapped just over a year ago. A local-ish shop did about 80% of the work, but when they couldn't complete it after 5 months(!) of waiting and with all of the uncertainty over lockdowns at the time - we trailered it home and my brother-in-law and I finished it ourselves. The list below are most of the parts we installed and changes that were made. I may be forgetting a few things, but this should be the relevant information.

  • 2ZZ
  • 2001 Celica GTS ECU
  • MWR CAI
  • PPE header
  • PPE high flow cat
  • PPE/Magnaflow dual-outlet exhaust
  • New spark plugs
  • New Denso coil packs
  • New IACV
  • New lift bolts
  • Thoroughly cleaned throttle body
  • Polarity switched on the throttle position sensor and sensor replaced with a unit from NAPA

The car ran great and pulled really hard when in lift. Eventually the timing cover gasket (not the tensioner, the actual timing cover) started leaking oil. We elected to remove the cover with the engine still in the car and replace the gasket. Some things likely got jostled during all of this, but the job went mostly well. After all of this work, I started getting the P0301 code, which is sometimes accompanied by the P0300 code. The car (mostly) runs great and it pulls hard when it lift, but it feels a bit sluggish and slow to respond at low RPM and light throttle openings. Below are some of the things I have done to help solve this.

  • Replace spark plug in #1 cylinder (second time)
  • Replace ignition coil in #1 cylinder (second time)
  • Remove and inspect fuel pump assembly for any obvious cracks or damage
  • Search for vacuum leaks
  • Re-bleed the cooling system
  • Fix a questionable ground from the battery
  • Get frustrated while trying to read the large number of threads on this topic

Even after reading all of the threads, I am not sure where to go next. If I disconnect the battery overnight, I can drive the car for awhile without the check engine light coming on. The next time I start the car and begin to move, the light comes back. The idle is very high (around 1200 - 1500 RPM) but it will usually settles down to around 900 - 1000 RPM if I drive the car for 10 - 15 minutes.

My code reader allows me to read the long term fuel trim for bank 1 and 3, but the bank 3 value is always zero. I'm not sure if this is correct.

LTFT 1 minutes after cold start idle: -5.5
LTFT after a 15 minute drive and at idle: -6.3

I realize that it is bad form to re-ask a question that has ben asked so many times in the past, but it seems like the resolution (if there is one) is not consistent for this problem. I'd really like to get this resolved and start enjoying this car again.

Thank you.
Jim

83013




83014
 

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Generally I'd go after a Fuel Injector.. Except your Getting a High Idle.. TWO Problems?..

What Intake?.. and What Color Injectors..

Pull the Injectors and have them Tested and Cleaned.. see where the Flows are .. We just want them to Match..

High Idle MIGHT be a Sluggish Idle Air Control Valve.. It's a Servo Driven Air Leak that Bypasses air around the T Body to allow the ECU to Speed up the Engine at Idle Speeds.. Generally IAC Problems do not toss the IAC 500 Code.. But it should.. Something like the P0125 Code that says the Coolant Temp is Low.. But that code really is an O2 Sensor code!.. Go Figure..

Aftermarkett Intakes tend to make the Engine Run Lean.. It's a Trick to get the Ignition to Advance sooner.. SOMETIMES on the 2ZZ Swap, Brown Injectors cause a Lean Stumble.. However your Idle Trim is -6.. so at least the AVERAGE of all the Injectors is Rich at Idle .. But 'WE' don't know where the Mixture goes on the Off Idle Transition..

I've got a Scann Tool that reads live data.. when I hook it to my '97 Ford Aerostar, it says I have TWO main O2 Sensors, and it Gives me Garbage on the Second One.. The '97 Aerostar only has ONE Main Engine O2 Sensor.. So not all scan tools really know what they are doing..

Please post what you find..

Cap
 

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Because of all the messing around on the front of the engine during the change I would check the wiring of the crank and cam sensors for damage. Also the tension of the timing chain.
 

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Discussion Starter · #4 ·
Thank you both. I have the yellow injectors and the MWR intake. I've never touched the injectors, so it wouldn't surprise me if they have issues. I will also double check the wiring.
 

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2003 MR2 1ZZ
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Well not being a mechanic I am not certified or anything. I was in a similar situation were I was getting random misfire codes and misfires on all the cylinders so P0300-p0304 and I took my IACV apart and found it was stuck in one position and not rotating as the engine warms up. It might be worth taking apart and servicing.
 

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Discussion Starter · #6 ·
Well not being a mechanic I am not certified or anything. I was in a similar situation were I was getting random misfire codes and misfires on all the cylinders so P0300-p0304 and I took my IACV apart and found it was stuck in one position and not rotating as the engine warms up. It might be worth taking apart and servicing.
That is a good suggestion on the IACV. We did replace it with a new (OEM) unit last year, but it would be good to look it over again.
 

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Although my car has a 1zz, how I solved my misfire woes was changing the fuel injectors, cleaning the MAF sensor and checking for damage on the ignition coils.
 

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Although my car has a 1zz, how I solved my misfire woes was changing the fuel injectors, cleaning the MAF sensor and checking for damage on the ignition coils.
I am about to start my car up soon just waiting for a valve cover bolt that was special ordered. If my misfire still occurs i will try injectors.
Happy you are back on the road.
 

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Discussion Starter · #9 ·
Although my car has a 1zz, how I solved my misfire woes was changing the fuel injectors, cleaning the MAF sensor and checking for damage on the ignition coils.
Working on the injectors now. Will post back when that is finished up, but it may be a few weeks. Glad you solved your issue!
 

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Well not being a mechanic I am not certified or anything. I was in a similar situation were I was getting random misfire codes and misfires on all the cylinders so P0300-p0304 and I took my IACV apart and found it was stuck in one position and not rotating as the engine warms up. It might be worth taking apart and servicing.
what do you mean by servicing? I read everywhere of people just replacing.
 

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It is possible to dissemble the IAC and clean the rotary valve that gums up. Personally for the long haul I think it is better to replace with a new Denso unit. There are many manufacturers of these units.
 

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Working on the injectors now. Will post back when that is finished up, but it may be a few weeks. Glad you solved your issue!
jimt - Were you able to solve this? Did you replace, clean, or swap the injectors around and did it make a difference? I am having the same issue on my recent 2ZZ swap and also getting frustrated.

My car also has a high idle and runs rough when cold, but runs much smoother when up to temp. Going to double check my AICV isn't stuck after cleaning it too.
 

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servicing injectors means sending the set out to a place like Marren. You get back a set of cleaned and flow-matched injectors
I was referring to the IACV, although since then I have learned you can take it apart and clean it if you are careful. (and can extract the soft screws with the odd 5-pointed drive)
 

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I feel your pain. I had the exact same experience after a faultless mechanical 2zz swap. I bought the complete MWR kit, including harness adaptor, intake, and swap header. The 1zz prior to the swap ran perfectly with no codes. like you, I found plenty of similar posts, but never found anyone that posted a definitive fix. So I'm going to change that. Of course, I can't be certain the my fix will work for you, but after all the testing and research I did, I'm confident what I found should be applied to all 2zz swaps that use the MWR intake, at least the latest version they are selling. The solution is here: 3.5 Mass Air Flow Straightener Honeycomb Screen | Performance MRP. I believe what is happening is random excess turbulence in the intake air flow caused by the proximity of the emissions intake port to the MAF. This turbulence affects the MAF intermittently and randomly enough to create random and intermittent misfires that have very little effect on the actual performance and driveability, but enough to record grey codes, that eventually set the CEL. I could drive for usually tow days without the CEL, but was getting grey codes for misfires fairly often, especially with a cold engine. This turbulence can also affect the AF ratio as well causing lean/rich grey codes. This likely isn't an issue with every 2zz swap due to some subtle variability in the physical installations by different owners, but if you read the info on the Performance MRP website, it makes sense. I can recall older cars I owned when EFI and MAF sensors were new tech that had honeycomb air flow straighteners built into the intake air flow. There were warnings not to stick anything inside that would damage the honeycomb. After the purchasing the honeycomb, I was able to take before/after fuel trim readings and verify the improvement. And I repeated the process more than once. The readings are exactly where they should be (less than 3%) and no codes of any kind being set. However, one other caution I would make, and that is if you are using the MWR swap header, plug both O2 sensor ports and get a bung welded just after the factory collector for your pre cat O2 sensor. As others smarter than me have indicated, the OEM ECU algorithm was created for this configuration and will not control combustion properly using the MWR recommendation. During my troubleshooting process, I had numerous email discussions with the MWR tech, and tried everything they recommended and more, and in the end, they were no help. I think it's because they would have to change all their advertising and fess up about some of their less than ideal engineering for the intake and their stance on the O2 sensor placement. I can see why some people don't care if the have grey codes and CEL, and some may get the swap to work without these issues, but it's real easy and inexpensive to add the honeycomb and it worked for me and my bet is it will improve performance for every swap even if no codes are being set. And of course, hers's the standard disclaimer that I have no affiliation with Performance MRP other than as a satisfied customer. Anyway, sorry for the long post. I've been wanting to get this info out for a couple of months, but just haven't thought about it until reading this post.
 
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