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Old 11-17-2015, 11:18 PM   #1
foxboysracing
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92 Accord LX to 93 EX questions

Hi,
I have a 92 Accord Lx with 480,000 original miles. It blew a head gasket and rather than rebuild the head(it needed it), we found a used engine with 150,000 miles on it. The engine is in and runs well. We used all of the external parts from my car. The engine came out of a 1993 EX car. The engine is fundamentally the same right? (I had originally thought they were an identical engine. oops) What are the differences that might cause these issues?
My concerns are:
The check engine light comes on at about 35-40 mph and stays on. The car runs perfectly fine. I wonder if the sensor from the engine I put in is not communicating with my computer like it should. Any ideas?
The tach is being weird. At idle, the tach shows 0 rpm's and yet the car is idling fine. The tach does not appear to be accurate anymore. It goes up and down like it should, but seems to be off some.
It does have the erratic idle issue. I am not worried about that. We have fixed that before. No real issue there.

Any ideas??
I tried to read the CEL codes and cant find the little plug on on the passenger side kick panel area.
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Old 11-18-2015, 01:46 AM   #2
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Not having the right ECU got the engine can cause symptoms like you described.

IIRC the 93 EX could have came with a F22a6 which requires the PT6 ECU to run correctly.
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Old 11-18-2015, 07:36 AM   #3
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Quote:
Originally Posted by Flip-Eye View Post
Not having the right ECU got the engine can cause symptoms like you described.

IIRC the 93 EX could have came with a F22a6 which requires the PT6 ECU to run correctly.
This exactly. An ecu from the ex should fix all of those problems.
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Old 11-18-2015, 07:45 PM   #4
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Agreed. Although if you want the IAB to work properly, you need to run a wire from the IAB control valve through the bulkhead to the ECU and a second wire to ground.
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Old 11-18-2015, 07:54 PM   #5
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^^^^^^^^^^^^^^^
The ECU provides ground in that circuit. The other wire goes to switched 12volts.
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Old 11-18-2015, 10:50 PM   #6
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Thank you. So, I was told that the engine was from an EX. I just went and checked on the front of the engine and it says F22A1, NOT F22A6. So hmmm? Maybe its an LX engine? We used the exhaust, my FI (intake?) and the distributor.
Now I am not sure.. What all does the ECU communicate with? With these changes in my situation, would you still say it needs a different ECU? I bought the engine at the wrecking yard. Would it be smart to go and get the ECU out of that same car, so it all matched and communicated?
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Old 11-19-2015, 08:49 AM   #7
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Your LX came with the F22A1 from the factory so you shouldn't need a different ECU.

I think the key to finding your problem is to find the CEL connector. You will need those codes.
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Old 11-19-2015, 09:19 AM   #8
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For anyone who reads this in the future needing similar help:

A situation in which an F22A1 long block is replaced with an F22A6 long block will not cause a check engine light, all else being equal. At that point, the only difference is the camshaft and it's not that drastic. People swap in Delta camshafts into their F22A engines with no CELs all the time. Why would it suddenly do it with a slightly more aggressive OEM camshaft? This is also to say that you wouldn't need a different ECU (under the previously-mentioned scenario). The PT6 ECU, while it is the correct ECU for that camshaft, will also be looking for the IAB hardware, which a longblock replacement wouldn't have. Sure you could upgrade for the sake of full compatibility, but that's not what was discussed here.

So, if you had a CEL under this scenario, something must have been installed incorrectly, or there is a bad bit of hardware somewhere on the replacement engine. You've now clarified that the engine is, in fact, not an F22A6, but the same F22A1, compatibility issues should not be present. It sounds like you have some bad hardware somewhere.

The very first bit of advice given to you should have been to keep looking for that plug. It's there. Let us know once you've found it and read the code.

And before you come back to post that it's not there, it is. Keep looking.
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Old 11-19-2015, 10:32 AM   #9
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Quote:
Originally Posted by foxboysracing View Post
Thank you. So, I was told that the engine was from an EX. I just went and checked on the front of the engine and it says F22A1, NOT F22A6. So hmmm? Maybe its an LX engine? We used the exhaust, my FI (intake?) and the distributor.
Now I am not sure.. What all does the ECU communicate with? With these changes in my situation, would you still say it needs a different ECU? I bought the engine at the wrecking yard. Would it be smart to go and get the ECU out of that same car, so it all matched and communicated?
The engine you removed from your car and the engine that replaced it are both F22A1 engines. That means they are EXACTLY the same. Every single bit should be 100% identical.
As Jarrett said, either something is broken, or something isn't hooked up properly. Find that plug and pull the code. The plug is there. It may be wrapped in tape if it has never been used before.

We can't help you any further until you find that plug and pull the CEL codes.
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Old 11-19-2015, 08:35 PM   #10
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Quote:
Originally Posted by djcaz_aom View Post
^^^^^^^^^^^^^^^
The ECU provides ground in that circuit. The other wire goes to switched 12volts.
Right. I said it backwards.
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