94 Mazda MX-3 Surging

Reply

  #1  
Old 07-21-17, 12:00 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 9
Received 0 Votes on 0 Posts
94 Mazda MX-3 Surging

1994 Mazda MX-3
1.6L 16V DOHC
50,000 miles

Vehicle was parked unused for 9 years under a carport. In 2015, brakes, battery and fuel pump were replaced and vehicle resumed service. Initially, vehicle ran well, but seemed slightly lacking in power. After 6 months, a rough idle was noticed, with the vehicle exhibiting what seemed like an intermittent misfire at idle.

At this point the spark plugs, plug wires and distributor rotor were replaced without a successful resolution to the problem and the misfire grew worse.

Eventually, the Check Engine light started blink codes for the Mass Airflow Sensor and the Throttle Position Sensor. Both were replaced which caused the Check Engine light to stop, but did not have any effect on the idle or lack of power.

Recently the transmission HOLD light began flashing from time to time. This resulted in the Transmission Speed Sensor being replaced, but did not resolve the flashing HOLD light. Transmission fluid was replaced, but still no resolution to the flash of the HOLD light.

Within the last 3 months, an Oxygen Sensor (Inversion) code from the Check Engine light and the engine will not rev past 2400 RPM. At 2400 RPM it will drop RPMís and then surge back to 2400, drop and surge, drop and surge, until the throttle is released. Sometimes there will be a backfire through the intake. If the throttle is just at 2400, the surge cycle is slow, if the throttle is opened wider, the surge cycle is faster.

O2 sensor replaced, throttle body removed and cleaned, EGR valve tested, checked for vacuum leaks and inspected vacuum hoses, still surging. While the Check Engine light for the Oxygen Sensor (Inversion) has stopped, the codes for the Mass Airflow Sensor (08) and the Throttle Position Sensor (12) have returned.

Lee
 
Sponsored Links
  #2  
Old 07-21-17, 04:24 PM
Banned. Rule And/Or Policy Violation
Join Date: Jun 2017
Location: USA
Posts: 785
Received 0 Votes on 0 Posts
An IAC comes to mind. It sounds like it's sticking.
 
  #3  
Old 07-21-17, 06:57 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 9
Received 0 Votes on 0 Posts
Thank You,
I've taken the throttle body off and what AllData describes as the Idle Air Control Valve and sprayed throttle body cleaner around. I also moved the valves with a small screwdriver and tested per AllData. I haven't put it back together yet, I'll do that tomorrow.
Name:  BAC.jpg
Views: 176
Size:  46.7 KB
 
  #4  
Old 07-21-17, 07:01 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 9
Received 0 Votes on 0 Posts
Also,
Iíve found that if I rev it immediately upon starting, it will rev beyond 2400. However, once the RPMís drop below about 2700, it starts the drop and surge process. Ironically, itís idling great.
 
  #5  
Old 07-21-17, 07:18 PM
Member
Join Date: Aug 2015
Location: USA
Posts: 483
Received 7 Votes on 7 Posts
not sure if this vehicle has a rev limiter but not uncommon for vehicles to have them witch would result in surging if your revving the engine in neutral or park.
does the air intake hose look ok any cracks or splits that could be causing the mass airflow code?
does it surge while driving also have you had it to a shop or garage for diagnostic.
 
  #6  
Old 07-21-17, 07:35 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 9
Received 0 Votes on 0 Posts
I don't think it has a rev limiter. Iíve found that if I rev it immediately upon starting, it will rev beyond 2400. However, once the RPMís drop below about 2700, it starts the drop and surge process.

I have examined all the hoses and rubber parts and have found no cracks. The hoses are slightly stiff, but still pliable.

I have taken it to a garage, 3 or 4 times, and they keep coming up with MAF's and TPS's and speed control sensors and within seconds of driving off their lot, the symptoms return.

So, I deduced that they were not testing their work and decided to try and tackle this myself.

I can't even get a Mazda service department to return my calls.
 
  #7  
Old 07-21-17, 07:56 PM
Member
Join Date: Aug 2015
Location: USA
Posts: 483
Received 7 Votes on 7 Posts
would probably try another independent shop one that will take it for a drive see what the vehicles doing and see about getting another diagnostic done if the symptoms don't occur all the time, you may need to leave it with them for awhile sometimes it can take awhile for them to see the problem and figure out what is causing it. there is a lot more to it than just checking codes.
 
  #8  
Old 07-22-17, 04:18 AM
pugsl's Avatar
Forum Topic Moderator
Join Date: Mar 2008
Location: Raleigh, NC
Posts: 8,482
Received 25 Votes on 24 Posts
look for a vacuum leak. lightly spray starter fluid around running engine and where engine revs up leak is in that area. Leave air cleaner on to try first.
 
  #9  
Old 07-22-17, 06:23 PM
ukrbyk's Avatar
Member
Join Date: Mar 2010
Location: USA/ Pacific NW
Posts: 3,485
Received 5 Votes on 5 Posts
1. air leak somewhere. Metal expands and gaps open as it warms up. Do the brake cleaner spray thing.
2. EGR. Does it have a LONG pipe attached to it? That pipe gets clogged with carbon build up and causes erratic idle. You "tested" EGR? Did you actually clean it?
Error codes confirm that your issue is somewhere related to air fuel mix. Air leak.
 
  #10  
Old 07-29-17, 05:13 AM
Member
Thread Starter
Join Date: Jun 2014
Posts: 9
Received 0 Votes on 0 Posts
Thank you to all!
I have replaced the computer with a used one from Ebay, and the issue seems to be resolved. I can now rev past 2400, however, there is still a dead spot around 2400 where it wants to drop a bit, but pressing the accelerator pushes the RPM's on up. I'm going to work on adjusting the TPS today, as I understand, it needs to be fairly precise in its position.

Thanks again!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description: